It’s early days so things are in flux. Communities will stabilise as they scale. I think people coming from Reddit misunderstand the Fediverse; I know I did - there does not need to be just one “federation” - some communities will be linked together in one federation and others will sit in their own separate instances or federations.

I think it’s likely there will be one (or more) large dominant popular/mass fediverse with a broadly shared ethos - and that currently looks like servers like lemmy.world, lemmy.ml, kbin.social, fedia.io etc - and numerous other smaller or focused fediverses of various sizes. Beehaw seems to be going that route at present for example (or at least until some of it’s concerns around moderation can be vetted). Once that alignment takes shape and communities mature, members of a broad federation would be disincentivised from defederating from each other.

The BeeHaw communities were larger and attracted people as they’d been longer established, but people swamped them and the moderation tools and vetting tools aren’t in place for Beehaw to maintain it’s ethos. I suspect it won’t federate in the near future with big instances (and I applaud that as their focus seems to growing their community more organically around their ethos), and in terms of users they’ll probably grow more slowly than the others. The large open Lemmy & Kbin communities in other servers are more likely to attract growth, but at present they’re chaotic and not established as communities.

Stability and reliability in terms of federation will grow out of this. New servers for example are going to likely want to federate with the established big Lemmy and Kbin servers as thats where the users are and so hopefully will be the content.