What are their alternatives? I'm assuming that most of the 22k people with large audiences that need a large platform to reach them. Meta unfortunately, is the only platform that allows people to reach across many demographics. Its the people that follow the 22k accounts that are important, and they are unaffected by this and thus aren't leaving meta (and 99% won't even know this happened or care).

Depends on the use case, but TikTok is an alternative for many of them, I would say it generally feels more like the place where interesting things are happening vs. meta properties.