I just want to add, that they (FB and other big social media) probably understood what propaganda power they wield after 2016 facebook and cambridge analytica scandal.

Personally - I think that this was the moment when silicon valley billionaires without shadow of a doubt understood that they have power what used to be reserved only for state actors. Bonus - for using that power they get fined penny on the dollar at most or just slap on the wrist.

Update: now situation is even worse - states actively buy propaganda with social media companies, making those companies even more rich and influential.