Why didn't Jaime Lannister tell everyone about Aerys's wildfire plans?

Question

Jaime Lannister killed King Aerys II, the mad king, a man he swore to protect, to stop the king from burning the city with wildfire. He never told anyone why. Not even his father or his sister. Perhaps not even the other knights of the Kingsguard. (Do the other knights know why?)

He finally told Lady Brienne of Tarth.

“Has my tale turned you speechless? Come, curse me or kiss me or call me a liar. Something.”

“If this is true, how is it no one knows?”

“The knights of the Kingsguard are sworn to keep the king’s secrets. Would you have me break my oath?” Jaime laughed. “Do you think the noble Lord of Winterfell wanted to hear my feeble explanations? Such an honorable man. He only had to look at me to judge me guilty.” Jaime lurched to his feet, the water running cold down his chest. “By what right does the wolf judge the lion? By what right?”

I find his explanation odd. The guard is sworn to keep secrets, but there is a difference between a secret about how many women the king enjoyed last week and a command to burn down a city full of innocent people.

Jaime could easily have told everyone. Anybody who knew the Mad King would have believed Jaime. Everyone knew Aerys roasted men alive in their own suits of armor. They knew he killed even powerful men who disagreed with him. People near the Mad King probably heard him yelling the same command for hours, "Burn them! Burn them all!" Those in the court (e.g. - Varys) could have corroborated Jaime's story.

He's much like Severus Snape in that he had to hide his best deed and let others call him a villain. But had he spoke, Jaime would have been seen as a hero, not a villain. He would have been forgiven instantly for his decision to slay the king. For a society that values honor, they would understand Jaime was torn between an oath he made and the desire to save half a million lives.

Do the books provide more insights into his decision to keep quiet?

Answer 1

First off I think it's worth pointing out that this appears to be an occasion when Jaime is actually telling the truth about why he killed the Mad King. Apart from my reading it as being true and Nikolaj's amazing scene from the show; we also have the corroborating evidence from Dany in the House of the Undying.

Finally a great pair of bronze doors appeared to her left, grander than the rest. They swung open as she neared, and she had to stop and look. Beyond loomed a cavernous stone hall, the largest she had ever seen. The skulls of dead dragons looked down from its walls. Upon a towering barbed throne sat an old man in rich robes, an old man with dark eyes and long silver-grey hair. "Let him be king over charred bones and cooked meat," he said to a man below him. "Let him be the king of ashes." Drogon shrieked, his claws digging through silk and skin, but the king on his throne never heard, and Dany moved on.
_{A Clash of Kings, Daenerys IV}

The traitors want my city, I heard him tell Rossart, but I'll give them naught but ashes. Let Robert be king over charred bones and cooked meat. The Targaryens never bury their dead, they burn them. Aerys meant to have the greatest funeral pyre of them all. Though if truth be told, I do not believe he truly expected to die. Like Aerion Brightfire before him, Aerys thought the fire would transform him . . . that he would rise again, reborn as a dragon, and turn all his enemies to ash.
_{A Storm of Swords, Jaime V}

I think Jaime gives his real answer for why he told no one in the quote you used, no one would believe him. Seeing as the man coming to lift the siege was Eddard Stark, known for being honourable, he'd be less likely to convince him of the truth. Though he didn't know it was Ned until he got there.

"The knights of the Kingsguard are sworn to keep the king's secrets. Would you have me break my oath?" Jaime laughed. "Do you think the noble Lord of Winterfell wanted to hear my feeble explanations? Such an honorable man. He only had to look at me to judge me guilty." Jaime lurched to his feet, the water running cold down his chest. "By what right does the wolf judge the lion? By what right?" A violent shiver took him, and he smashed his stump against the rim of the tub as he tried to climb out.
_{A Storm of Swords, Jaime V}

This seems all the more true when you consider that he hunted down and killed all of the pyromancers. If he believed they would support his story he would not have had to do that. He probably also thought them so loyal to Aerys that they'd still go through with his plot. With that in mind I'm sure they wouldn't have helped him out.

"When I came on Rossart, he was dressed as a common man-at-arms, hurrying to a postern gate. I slew him first. Then I slew Aerys, before he could find someone else to carry his message to the pyromancers. Days later, I hunted down the others and slew them as well. Belis offered me gold, and Garigus wept for mercy. Well, a sword's more merciful than fire, but I don't think Garigus much appreciated the kindness I showed him."
_{A Storm of Swords, Jaime V}

With the pyromancers dead he probably didn't know where to find the wildfire caches to help in his story so kept quiet.

Lastly, it is worth considering Jaime's attitude. He is a Lion of Casterly Rock, a member of the Kingsguard and an expert swordsman. With all that he is cocky and so seeing as he assumed no one would believe him he took on that persona even more. He climbed onto the Iron Throne with his bloody sword and waited for whoever it was to come and claim the throne.

"Shall I proclaim a new king as well?" Crakehall asked, and Jaime read the question plain: Shall it be your father, or Robert Baratheon, or do you mean to try to make a new dragonking? He thought for a moment of the boy Viserys, fled to Dragonstone, and of Rhaegar's infant son Aegon, still in Maegor's with his mother. A new Targaryen king, and my father as Hand. How the wolves will howl, and the storm lord choke with rage. For a moment he was tempted, until he glanced down again at the body on the floor, in its spreading pool of blood. His blood is in both of them, he thought. "Proclaim who you bloody well like," he told Crakehall. Then he climbed the Iron Throne and seated himself with his sword across his knees, to see who would come to claim the kingdom. As it happened, it had been Eddard Stark.
_{A Storm of Swords, Jaime II}

Answer 2

I have read the books multiple times but not seen the entirety of the TV Show even once. The reasons Jaime never tells anyone about the wildfire plans is-

1. It is pointless without definite proof

Everyone who likes/supports him will believe this and think him a hero; everyone who dislikes him or wants to see the Lannisters fall will take it to be a self-serving lie. His father had defected from the Targaryen side AFTER the war was almost decided. So his actions would have looked opportunistic. This refutes:

"But had he spoke, Jaime would have been seen as a hero, not a villain. He would have been forgiven instantly for his decision to slay the king. For a society that values honor, they would understand Jaime was torn between an oath he made and the desire to save half a million lives."

Varys may not have corroborated his story. It is quite possible nobody heard Aerys' words as that was said to Rossart not in normal court.
The same happens regarding the 'truth' content of Stannis' proclamation throughout the realm-

Catelyn had a glimmer of understanding. "Stannis means to parade his brother's bastard before the realm, so men might see Robert in his face and wonder why there is no such likeness in Joffrey."

"Would that mean so much?"

"Those who favor Stannis will call it proof. Those who support Joffrey will say it means nothing."

_{A Clash of Kings, Catelyn VI}

Also, while Targaryens are known to be a bit mad, they still hold love/respect in many houses and by many smallfolk through Westeros (known example-Darry).

2. The Oath

Honorable lords like Ned Stark (and most other lords if they wanted to be politically correct) would have expected Jaime to at least not kill the King he was sworn to defend. The urgency of Jaime's situation (to protect the city from burning in wildfire) would not have mattered to them in hindsight.

3. Jaime's youth and nature

Jaime never claimed to be righteous, he did what he thought was right and what was his natural instinct in killing the King but he never claimed to care about anyone but his family. Why would anyone believe he wanted to protect the city from wildfire. Jaime is always portrayed as impulsive in everything, so his actions during this time also were impulsive and not the result of reasoned argument.

4. Issue of loyalty

Even knights like Arthur Dayne stayed loyal to the Throne despite Aerys II's madness. So it would be hard to believe his actions were not merely opportunistic and were (partially) forced. (He did defect by choice but he had good and sufficient reasons according to his thinking).

---

Also it may be that he did not know who will win the fight at Kings Landing so if Aerys II had been just imprisoned/held alive till then someone may have saved him/helped him escape (Varys?) and the whole realm would have bled in answer (including the Lannisters, who Jaime loved). This happened after Tywin revealed his allegiance in the Sack of King's Landing.

Any reason Jaime would have given would have sounded like an excuse, and would have implied that Jaime's actions were wrong (which he did not believe they were), but why would a proud Lannister give any excuse to anyone else, let alone a Stark.

That leaves only personal contacts for Jaime to tell the truth to-

1. Kingsguard- Only Kingsguard alive (Ser Barristan) never asked for Jaime's side of the story and judged him to be an oathbreaker (which he was,to be fair) so there was no reason for Jaime to tell him the truth. Or any of the new Kingsguard (Jaime also considers them inferior). I expect he may have spoken to Arthur Dayne (who seems to be the only father-like figure who he really respected).

2. Cersei/Tyrion- Maybe he did tell them, we really can't say from the books.

3. Tywin- It is possible Tywin never asked Jaime if he had a reason. He may have expected Jaime to act in a way that was best for the Lannisters and killing the king worked out fine with Cersei becoming queen.

The book does not provide with any insights other than the quote mentioned in TheLethalCarrot's answer.

He only had to look at me to judge me guilty." Jaime lurched to his feet, the water running cold down his chest. "By what right does the wolf judge the lion? By what right?"

_{A Storm of Swords, Jaime V}

Answer 3

The books don't really provide more info about this. But I think that we can reasonably infer the answer from what we’ve seen nonetheless.

Granted, Jamie is a bit of a rogue (I'm trying to stay kid-friendly in this answer). But we the audience are aware of how seriously he actually takes his oaths, especially as KingsGuard. In a world of oaths, you poison your word if you break your oath. So he is absolutely right that nobody would have believed him; he had just broken his oath, people would think he would come up with any excuse to justify his actions.

Bear in mind that he is still getting crap twenty years later about killing the king that they were rebelling against, who was widely acknowledged absolutely and completely insane. That is how seriously these people take oaths.

If you are familiar with the fable about The Boy Who Cried Wolf, it's similar to that. He broke his oath, and nothing he can do would redeem him. There are real life examples of people historically going to great lengths to fulfill an oath and take vengeance, who are seen as honorable for doing so.

And note that he's also right about Eddard Stark, who is portrayed as the honorable, noble person we expect and want in a position of power. And we see how rapidly he is removed from power, the implication being that his rigid ethics were actually unsuitable to the job he was handed. Ned Stark is portrayed not only as the kind of aristocrat that we the audience want to see, but more importantly one who lives up to the standards of the world around him, rigid in his code of honor. So his reaction is a microcosm of the reaction that much of the world will have had.

Contrast this with the moral philosophies of many of the aristocrats, who are more than happy to set aside their morals in order to claw their way up one more rung on the ladder of power. They are clearly shown as the minority, or at least the minority in being effective at it. Look at how effective the High Sparrow is, and how difficult he is to unseat, because he is fanatically rigid in his ethics, and in doing so gathers a large base of power.