This isn’t really a federation problem, and more that there isn’t a clear “winner” yet.

Even on centralized platforms, you end up with multiple communities for the same topic, until one of them grows enough to beat out the rest. Then eventually a scandal might cause it to fragment again. There are also separate communities that keep going independently because of ideological differences. See the various international news subreddits

The movies communities here were like that, but now there is a pretty clear “main community”