You have to look at in the context of the 2016 election. Once it was discovered that the winning team utilized Facebook in a way the losing team had no concept of (or more likely they simply didn’t use said concept as effectively), Facebook has been singled out and targeted by most media outlets for being evil and in need of strict government regulations, to protect the children and democracy and society, among other things.
Yes, FB had negative press prior. But this was the clear turning point in press coverage and governmental oversight and it was like a light switch.
I can’t say I’m disappointed in the slightest about that, or that they’re wrong. I despise Facebook. But I do find the reasoning behind this all a very disturbing extension of the “cancel culture” we’re in today. The establishment doesn’t like not having a monopoly on the spread of information, and it is fighting back.
Besides, there are only a few sites that most people ever visit. The internet is “small” now. Tackle the biggest threat, the rest will fall in line - likely with glee since they already enforce pro-establishment censorship policies as it is. Twitter, for example.
If FB's business model were significantly different and didn't depend on maximizing eyeballs-on-screens time, and didn't depend on selling the ability to manipulate people's emotions at scale, the product might be less toxic.
In summary, I think it's a cop-out to just say "humans bad." Yes, but the systems we create and participate in can and do influence human behavior in different ways. Facebook wouldn't be quite so toxic if there wasn't money to be made from the toxicity.
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.)