That's what happens to all alternatives at the start, only really the content that isn't suitable for the main platform migrates there. It requires a mass exodus because of something major, like what happened with reddit 3rd party apps or twitter/X & the block change , to get enough regular users there.

Lemmy literally exists because Dessalines, a "long time Marxist-leninist" decided that "Fuck the while supremacist Reddit admins" and made an alternative to host r/communism because reddit is run by an "anti-tankie scum".