Very Online (TM) people with large Twitter followings like Marcus Hutchins are coming to realise that it made Twitter a compulsion, and given an alternative are willing to ditch the Skinner button [0].
Compulsion and addiction is different from desire or pleasure. When we're offered meaningful alternatives, people often find more peace and happiness when they adopt them.
[0] https://infosec.exchange/@malwaretech/109368403091846997
I've set up my own BirdsiteLive instance that only my own Mastodon server can access, but it's slowly seeing less and less activity as people switch over to Mastodon or something I can't bridge.
Plenty of people are going to keep Twitter as their cesspool, but it'll be a while before everyone who wants to switch has switched. Musk's behaviour and the following downward trend for Twitter is still recent news, it's only been a few weeks.