Meta or any other big player that looks to ride on the fediverse space ultimately gets nothing that's not already available publicly, and can't push their ads or data-scraping apps on the users of the fedi. In effect they'll either play nice and maybe a few people interact between them, or they don't and things continue as they are today. There have been a couple posts out there of the history with Google/XMPP and now the statement by Mastodon. Private hosting of open protocols has always been a threat to the big players. In the end with the Google affair, XMPP still exists, I used to use it for my household chat, but found other options like RocketChat and now NextCloud Talk more to my taste and easier to maintain. Meta can't kill the ActivityPub system, only the users walking away from it can do that, or, I guess ISPs if they did some sort of shady blocking en-masse but that's another matter all together.
I have no use for Meta in any of their forms, and would certainly push others to use the OG version of things that doesn't scrape all their data to sell them the latest bullshit they don't need, but there's little reason to fear them either.