But it's a pretty plausible retcon that I could see Musk himself going for at some point.

The illustrative Calvin and Hobbes comic at https://tvtropes.org/pmwiki/pmwiki.php/Main/IMeantToDoThat demonstrates the principle rather well.

I don't disagree. I think he bought it on a whim because to show that he could, in the same way that a football fan might say they could run the team better than a manager.

Then he realized it was not in fact a good idea and backed out of it.

If a football fan actually does buy the team, and finds out they could not, in fact, run it better, they might amend their story to, "Actually I just thought it would be cool to own a team," in order to save face.

I think that's a more likely scenario: much like the hypothetical football fan, in a fit of zeal he said, "I could run this better!" If the goal were simply to flex his bank account, there are so many better ways he could have done that that I think we could safely assume he would have picked one of those instead. He may not be as smart as he thinks he is, but he isn't stupid.

I don't think it makes sense to apply you-and-I logic where actions have consequences to a billionaire. He obviously never had a business case that would make twitter worth the premium and extra billion dollars a year interest it's paying now.

So my point is not that he doesn't want it to succeed, it would obviously be a great personal embarrassment. It's that the risk of destroying a community of millions of people was clearly lower on his mind than the power trip of how cool it would be to own Twitter. He can afford to not care, and that's a deeply depressing situation.