The thing is (IMHO), fediverse communities are spread but they are not « fragmented ». That’s the beauty of it, no matter where they are, they’re not isolated from each other.
Forever it’s been like that, even before the internet. Communities come and go, and seeing them go can be sad… but when hosted centrally by large corporations, maybe those communities were not at a healthy place. In that case, the place dies, the communities go someplace else, I do hope they go to a healthy place like the fediverse, and they can live « prosper » (socially instead of financially)?