Why didn't the North (or anyone really) declare for Daenerys?

Question

In Season 6, some of the Westerosi lords

specifically, some of the Greyjoys

appear to be making plans for declaring allegiance to Daenerys Targaryen.

1. If this is something the nobles are willing to do, why haven't any done it earlier?

2. In particular, why didn't Robb Stark consider it himself?

I know that, at one point, Greatjon Umber made a comment about the Targaryens that:

It was the dragons we bowed to and now the dragons are dead.

Did people think Daenerys was dead? If so, was it based on Varys telling Ned that it was too late to rescind the kill order?

3. Ned, for his part, seemed determined to maintain the integrity of the line of succession, when he chose to support Stannis over Renly as King.

How is it consistent to choose Stannis over Renly but to choose Robert over Viserys or Daenerys?

Edit: Assuming R+L=J, it may make sense to not declare for Viserys or Daenerys

Answer 1

One thing that you have gotten wrong is:

Greyjoys are not pledging allegiance to Daenerys. Their plan is be her ally and make Euron Greyjoy her King Consort, thus becoming equals of the Royal dynasty and take over all the seven kingdoms. (Yara/Asha and Theon are dissidents and exiles, they are not legal representatives of Iron Islands and Greyjoys. Kingsmoot chose Euron as Iron King legally).

There is no support for Daenerys in Westeros among nobles generally because People mistrust her as Mad King's daughter and she left Westeros as a babe and thus has no allies. We saw this when Qartheen merchant Prince asked Daenerys if she has any allies in Westeros? And she replies that she left as a child. To that the Merchant Prince replied that means she has no allies.

Except Dorne. Martells are conspiring to get the Targaryens back but even they harbor doubts about her sanity (In books, in show they are wiped out)

We have seen this before that lack of contact with the nobles can deprive you of allies. King Aegon III's daughters were imprisoned by their Brother King Baelor I. They spent more than a decade locked in a tower. When their brother died childless, Princess Daena was heir of her brother but due to her imprisonment, she had no noble allies and crown passed to her uncle King Viserys II Targaryen.

Why should Robb Stark pledge allegiance to a girl lost in wilderness of the East when he has the chance to reclaim the Kingdom of his forefathers? Starks were Kings in the North for thousands of years until Aegon the Conqueror made King Torrhen Stark kneel and swear fealty to him. You answer yourself in the quote you cited:

MY LORDS! Here is what I say to these two kings! Renly Baratheon is nothing to me, nor Stannis neither. Why should they rule over me and mine, from some flowery seat in Highgarden or Dorne? What do they know of the Wall or the wolfswood or the barrows of the First Men? Even their gods are wrong. The Others take the Lannisters too, I’ve had a bellyful of them. Why shouldn’t we rule ourselves again? It was the dragons we married, and the dragons are all dead! There sits the only king I mean to bow my knee to, m’lords. The King in the North!

He is not talking about Metaphorical dragons, he is talking about real dragons. It was Vhagar, Meraxes and Balerion who made the Northmen join the realm of Aegon the Conqueror. Now all the dragons were dead and dragonriders were almost gone from the earth. Why should they be ruled by some Southern lordling any longer?

That does not mean Robb never considered allying with anyone in War of the Five Kings. He considered only the people with real power in vicinity as potential allies, Daenerys did not fit the bill. That is why he laments that he could have married Sansa to a Tyrell and allied himself with High Garden. He also tried to make an alliance with Renly Baratheon even though Robb refused to consider him King. He also tried to forge an alliance with Greyjoys for mutual assistance in both their independence.

The Lords of the realm gave their verdict on claim of Viserys and Daenerys when they crowned Robert as King and sent Stannis to dragonstone to arrest the deposed Princelings. Tyrells did fight for the Targaryens till the end but now they are allied to Baratheons due to marriage between Tommen and Margery.

Dorne did try to rise up for Viserys but Jon Arryn's diplomacy prevented that. (In books, show never depicted that era)

TL;DR, there is no incentive for the Nobles in declaring for Daenerys while the risk is enormous. Which is why even the most sympathetic nobles wouldn't rise for Daenerys unless she lands with her own power. The only people who are finding her and pledging fealty to her are the ones who have no other/better choice e.g. Tyrion, Jorah, Barristan, Greyjoy Siblings (In show) etc.

Season Six Finale Spoilers:

Dorne and The Reach have declared for Daenerys and joined her fleet sailing to Westeros. Fire and Blood is coming. Bear in mind, during Robert's Rebellion, Dorne and Reach fought till the very end for King Aerys. Though the reason they gave for their declaration is that they want vengeance for murdered Tyrells, Elia and Oberyn.

Answer 2

The reason they are considering such an alliance now, is because they hate all of the alternatives. As long as there was a chance that the Iron Islands would be able to rule itself, they were obviously going to take it. When they think that their choices have come down to Boltons or Lannisters, they're willing to consider other options.

---

The first thing to understand is that the line of succession, by itself, doesn't mean much. You have to have the power to support your family's claim to the throne (military, political, financial, etc.). When Ned is talking about the person who "should be" next in line, he's considering Robert seizing the throne as a legitimate transfer of power from Targaryen to Baratheon, because that's how things worked back then.

This is also the real meaning of Umber's quote. He's not saying all the Targaryen's are dead, because the nobles most likely know at least a few survived. He's saying that their power is gone -- the dragons they used to conquer Westeros are all dead, and without dragons, the Targaryen's can't hold onto power.

So, when the War of the Five Kings started, the Northern lords had a strong leader -- Robb Stark, leading their armies as the heir to Winterfell and the Stark name. There's no reason for them to consider allying with anyone else. At that point, Dany was just the last of a dying house, exiled across the ocean where she couldn't do anything.

The current situation with the Iron Island is very different. The Starks (as far as most people know) are dead, except Sansa, who's been married off to the Boltons. While the Starks might have been talked into a treaty of independence, the Boltons are on the verge of seizing the North, and they have shown to be significantly more ruthless than the Starks. To the south, the Lannisters have basically won the war and consolidated power. It's only a matter of time until one of them comes to finish the job. Meanwhile, more and more rumors are sneaking back across the ocean that Dany has conquered parts of Essos, has an army, and more importantly, has living dragons. The very thing that allowed her ancestors to conquer Westeros before, she has three of.

In that light, she begins to look like a really good alternative. Get into her good graces early, and when she takes over the continent, hope that she will forgive you for betraying her father.