Recent studies show that a very small percentage is responsible for some 97% of all tweets. And worse, 80% of those 97% of tweets are retweets.
There's almost no original content of any value on Twitter. You could now delete half of all Twitter users and absolutely nothing will happen.
Twitter is a bunch of celebrities/politicians saying things that fuel division and outrage, which generates the bulk of activity. They won't ban anything as because without Twitter richly rewarding them for idiotic takes, they are nothing.
maybe, maybe not. Mastodon & the Fediverse has been around long enough to establish itself as a Twitter-like "alternative". it's crossed the scope at which it's hard to get concrete numbers about how many people actively use it, but lower bound's around 500k MAUs across 10k instances. we get waves of new users _every_ time something controversial happens around Twitter. the largest instance (which accounts for about 15% of all users) gained 12k new users in the past week [1], so figure 50-80k across the board; some of which leave after a week, some of which properly embed themselves.
no, these aren't big-tech-co numbers, but it's a large enough base to be accommodating to certain types of today's Twitter users. not _every_ Twitter user cares about having 300M peers v.s. 500k peers, and bridging between Twitter and ActivityPub works ok enough to ease that a bit, especially if you were primarily using Twitter as a glorified RSS feed.