Ironically, Facebook was also involved with Google defederating from XMPP, according to an explanation I read many years ago (IIRC, from Larry Page when he was CEO). FB messenger could connect to Google Talk users, but not the other way around - so Google wasn't pleased about freely exporting users' "social graph"[1] to Facebook, and getting nothing in return.

1. The "social graph" was the new hotness then, everybody had to have it, just like AI now. An exec at Google convinced the company that Facebook was an existential threat, leading to some very questionable decisions bourne of a self-induced siege-mentality.