Misskey is a little bit odd, in the sense that there's constantly new forks in various stages of development. New forks emerge just as quickly as old ones die off.
It may be that the frontend and backend both being written in one language helps make the system easier to hack on. I can't say for sure. What's weird is that some of these forks go in really odd directions, like rewriting the whole backend in a different programming language.
The other thing is that, despite their proliferation, the effort is somewhat fragmented into all of these little projects. I'm not sure how viable any of these forks are in the long term.