That's what we are seeing, people are choosing one thing not a federation of things.
There needs to be some reason and big benefit that people get for choosing federation. The only thing I can see would be if there's some kind of major and controversial moderation defederation event (e.g. a cancel culture controversy) but very soon before people get entrenched in their patterns and can see why federations are useful.
Possibly then, having instances run by media organisations might actually show the difference in moderations in the fediverse.