That’s the problem. I can see a future where very few users and trolls “opt-in” to fediverse integration and for a while meta doesn’t rock the boat and actually contributes to the fediverse as a whole.
But Zuck would have us under ransom. All he has to do, if the fediverse starts threatening his business is turn on all accounts for federation, and it would quickly overwhelm the small independent operators. The fediverse would essentially be controlled by meta.