I see two possible ways for it to succeed:

• Federate by default, defederate if you have to. This is how Lemmy mostly seems to work; I proposed a policy for defederation for sh.itjust.works that has been used, we will federate with you unless you start spamming or hosting illegal porn or spewing hate speech or that kind of shit, then we’ll defederate. That has to happen at the instance level; if example.lol is generally fine but there’s one account there that’s a nuisance that’s what the block button is for, but lolita.rape gets defederated (and reported to the FBI).

• Apply and join model. Have a coalition of instances that agree to mutually uphold certain moderation practices (no hate speech, no kid fucking, goat or human, no human trafficking, etc) and then they federate with each other, eventually forming a large and wholesome community.

Nobody federates and it’s a bunch of independent nothings won’t work. Youtubers will use it as a backup service, a couple of the real paranoid Linux types will host their videos there that someone might even watch, and half the instances will be places you go when you’ve been kicked off of Youtube.