More likely global stock markets took a dive which devalued Twitter (and Tesla) substantially making the offer over-priced.

He should have hedged then. If markets have gone up, he would've reaped the benefits and Twitter wouldn't be able to back out.

well maybe he should not have offered a price based on meme numbers then.

This is true, speaking from experience with bipolar people close to me.

No psychiatrist would diagnose someone based on public performances, and non-psychiatrists using pop-psychology to do so is very unpleasant.

This is a wider cultural trend too. The prevalence of Dunning-Kruger pop-psychology YouTube videos (again made by people with zero medical degree) nowadays "teaching" people to recognize "Narcissism", "Psychopathy", "Mania", "Manipulation" etc. is absolutely vile. Just teach people assertiveness and leave it at that.

Hypermanic

there is no such this as “hypermania”

there is mania (Bipolar I) and hypomania (“lesser mania”) (Bipolar II)

And for anyone wondering, the difference between the two is the presence of psychosis.

I think it's a character thing for Musk, he's simply the kind of person who does things like this because he can.