The Fediverse is really not going to be relevant to Meta. It is too small, and is "built differently." Most instances distrust Threads, and while a few users might move, those migrations will be insignificant.
*Anything* they get from it is just a bonus.
They are competing with Twitter and Bluesky--where the money is. Bridging to the Fediverse through an "open" standard ActivityPub is the chrome on the kaka.
Zuck is trying to cash in on Musk's bungles. Even released early.