Twitter has a TON of active users though and those aren't going anywhere.

Hell, those that did leave Twitter did it to move to Bluesky which is basically Twitter under a different banner.

Even if people move away from specific instances of some form of technology (like Twitter, Bluesky, Mastodon or whatever) they are not necessarily moving away from the idea/tech iself (like microblogging in this example).

Same with other social media: notice how after "Reddit gone shit" the people who felt like that and did move away didn't move back to forums or whatever, they went to Reddit-like boards like Lemmy.