Consensus from those with closer experience is that he's always been kind of an asshole, just not a crazy asshole. Also, the whole "Elon's a Tony Stark genius" was literally a marketing campaign and he used to have a really good PR person. He fired that person some years back (want to say around '17-'18?) got on twitter and let that fully rot his brain.
I think this is a fairly predictable outcome when you fire anyone who contradicts you and seem to spend your whole day hotboxing your own farts with a legion of minions in tow who will stop at nothing to tell you what a great experience that is.