I find it hard to believe they are really going to join the Fedi. With 100 million users on Threads and maybe 2 million on the Fedi, how could Meta possibly benefit? Federating could bring them trouble but no benefit.
Also, isn't the 100M user figure disputed, because it's counting existing Instagram users or some such?
and when the EU complains, they get to throw their hands in the air and say "yeah, you made us do it"