The lack of answer to the question "Why are Meta suddenly so open and willing to integrate with the Fediverse when they've basically been doing the opposite with their own products?" is a huge concern.
My guess is that they don't have an exact game plan yet, and are letting their naive, enthusiastic staff - those with no idea of the answer to the above question - do the initial scout and integration work with a view to see how it can be perverted for Meta's profit/benefit in future.
Meta probably wouldn't use the word "perverted", but from an outside perspective that's what it'd be.
My thinking here is exactly the same as in comments I posted about Microsoft's embrace of Linux a short while back: 1 2