reiver, 
One thing that I think #Threads did well is that — they were able to bring over large chunks of communities over from #Instagram to Threads.
(They did it by pulling in users from Instagram to Threads https://mastodon.social/@reiver/110665875303226142 )
I think that this is one challenges the Fediverse has had, that affects retention.
One of the draws of a social-media network is the individuals and the communities that are there.