Twitter is great, but its the users that provide the value, not Twitter itself. If all the interesting people are moving to Mastodon, guess I'll need to move as well.
This is capitalism. He'd be completely within his rights to buy Twitter for cash...then completely shut it down, pay off A/P & such, and liquidate all assets.
Individuals in societies have this thing called reputation. Him claiming to supportive of free speech while doing this to a social platform he now owns is pure hypocrisy and damages his reputation, whatever's left of it.