If you think the laser focus happened "all of a sudden" I believe you haven't been paying enough attention. ;) I think outside of the U.S. there has been more concern about FB's awful track record for years by now.
But to answer your quest: For me it's their wish to be the biggest dog on Earth, aiming to be "everyone's internet" (especially in poorer, non-western nations) while at the same time wilfully ignoring the responsibilities that come with it.
Most other players are also bad, I guess, but so far not many of them are able to do that. much. damage. to society while putting profits first no matter the cost, while trying to game the system no matter the cost, while scorching the Earth to stave off perceived competition, while assuming they're above the law.
I'm certain that if Twitter, Telegram, Baidu, VK et al are having their own skeletons in the closet but they're not in the spotlight as much (yet).
(Edited for grammar.)