Why is Starscream second-in-command of the Decepticons?

Question

In the Aligned Continuity, it was revealed that

when Megatron first began spreading his revolutionary ideas across Cybertron for a just and equal society, Soundwave was chief among his followers, being by his side from the very beginning since before the war for Cybertron even began.

Starscream, however, was an Air Commander who joined the Decepticons only after the war began. During the war, he has already demonstrated a traitorous tendency towards Megatron. According to some literature, he has even alternated between staying neutral or even apparently working in favour of the Autobots at some point.

Clearly, Megatron has had a much longer history with Soundwave than Starscream, and his relationship with Soundwave appears to be quite personal too compared to a purely soldier-to-commander relationship with Starscream - Megatron often speaks of his personal thoughts and plans before Soundwave when they are alone, a demonstration of their special relationship at a level Starscream never enjoyed to the same degree.

As officers of the Decepticons, Soundwave has proven to be immeasurably more loyal to Megatron and reliable on missions than Starscream - two of the top qualities that Megatron values most in a Decepticon, as their one true lord and master. In leadership and skill in strategy and tactics, Soundwave does not appear to be inferior to Starscream either. Even if that is not the case, he definitely makes up for it with the lack of cowardice and tendency to panic that Starscream so often exhibits.

However I look at it, from my interpretation of Megatron's perspective Soundwave just seems more eligible as second-in-command of the Decepticons than Starscream in practically every way I can think of. The only possible reason I could find for why Starscream is made second-in-command is the fact that

Starscream captured Sentinel Prime and delivered him to Megatron instead of escorting him to safety with the Autobots, as an offering when he sought to join the Decepticons.

This act by Starscream impressed Megatron, but surely Megatron would feel that all that has transpired since then would not be worth whatever benefit or advantage he gained from Starscream? So why exactly is Starscream kept around as second-in-command, and Soundwave was apparently never considered for the post?

Answer 1

Regardless of which continuity I have seen so far (aligned and also a few of its predecessors), Starscream joined the Decepticons while betraying his old allies.

Megatron himself is not dumb though. He knows 2 things. First that Soundwave will always stay loyal even if he is not promoted. Second that Starscream is power hungry and traitorous AND useful (to some extent). So what position is best than 2nd in command for him?

In this position Megatron can watch him, while Starscream feels important. Additionally Soundwave can watch Starscream without the later trying to assassinate him to obtain the 2nd in command position (which Starscream would else do sooner rather than later......he even tried time and again to assassinate Megatron himself to gain even more power). And Soundwave thus is in a position where he can warn Megatron or sabotage Starscreams attempts to undermine/do away with Megatron.

Also for Starscream the feeling important thing is quite important. He has such a strong ego that he needs that, in order to do his duty and ONLY betray his allies when pushed (else he would do so on a whim of a hurt ego even as seen a few times in different continuum episodes).

So all in all the 2nd in command is the best solution Megatron can come up with. As it brings him a capable warrior, someone he can punch and who comes back to still serve him while minimizing the risk of Starscream plans to gain command of the Decepticons. And as soon as Starscream is no longer more of an asset than a liability.....he will go the way of all things that displease Megatron.

What really is a wonder though is that Megatron thinks that Starscreams abilities/plus points outweigh his incompetence/failures. And thus that Starscream still lives (despite him always loosing). With Megatrons tendency to even kill loyal failures.....that is something of a mystery there though (and as far as I know not explained in any way in any continuum).

Additionally in many of the continuums Megatron somehow seems to be amused by Starscream AND his attempts to ursurp his position (although this is only an observation and interpretation, thus not part of the answertext above).

Edit: I found something as to why Starscream is not killed by Megatron and also what adds to his usefulness (and thus in the end why he ends up in the 2nd in command position). As stated in another question from here: Why didn't Megatron kill Starscream in G1? According to an answer there by Wikis Starscream is not as much a failure as I myself always perceived, but instead very good at his job.

Answer 2

Why is Starscream Second-in-Command?

Seniority - Starscream traditionally holds the rank of Air Commander in the Decepticon power structure. This airborne pre-eminence guarantees him a place in the High Command.

Confidence and Ambition - Starscream is one of the few whose arrogance and ego can compare to his leader's. He wields his position in the Decepticon ranks with gusto, never failing to remind his companions of his authority.

Brutality - The Decepticon leadership is enforced by violence and fear. Starscream has an appetite for brutality which makes him suitable in this way. He also possesses a formidable array of firepower to back up any threat.

So that Megatron can keep an eye on him - Given the former Energon Seeker's history of trying to off his leader, this position is most likely based on the principle of keep your friends close, and your enemies closer.

Why isn't Soundwave Second-in-Command?

He already has an important job - Soundwave is the head intelligence officer of the Decepticons, as well as one of Megatron's most trusted lieutenants

He is more of a follower than a leader - His loyalty to Megatron is beyond compare, following every order to the letter.

He represents insurance against Starscream's treacherous tendencies - Soundwave can monitor Starscream at close quarters and always remains loyal to Megatron.