Off the top of my head, not mutually exclusive; The usability will be easier and better than Twitter/Facebook. It will be much easier to monetize your content, kids wanna get paid. Canceled ppl with large followings migrate. Ppl seeking ID portability/ownership. Ppl and business seeking interoperability with other types of uses (more than social media).
Discussion
That's a fairly plausible confluence of events. I can also see Nostr at the very least in the medium term applying some healthy competitive pressure on big tech not to be so bad in all of those areas.