I don't really have an opinion about mr Musk or his intentions, but I truly fail to see any downside with this deal. Either he does in fact make the twitter platform a generally more positive/useful/pleasant/... experience, or twitter's function will eventually be filled by other apps, maybe even new ideas.
For one, Trump seems to finally be receding into the background, and I can guarantee he gets his account back when Musk takes over. That alone is enough to view this as a net negative.
Worst case, he runs it into the ground and we live in a world without Twitter. Win win.
I have a tough time imagining the other worst case not prompting regulation.
Maybe it overthrows our political system! I don’t know, there are certainly some politicians who command from Twitter and will be hurt or helped by Musk. (Probably, invariably, helped.) But that seems less likely than Congress creating a rule book and regulator for social media.
Why would it? People have been complaining about facebook/twitter/etc for ages and competitors haven't turned out to be less harmful. Why is the idea that Musk forces his values into Twitter and that this makes the platform worse not a possibility?