I don’t know (…or care, really) about USA so I’ll speak on more general grounds.
There’s a lot of stuff in social media that makes it a great soapbox for social manipulation:
low cost, wide reaching: it’s easy to be heard
decontextualisation: it gives more room for assumers¹ to do their shit, and make an incorrect context out of nowhere.
virality: it’s easy to start a witch hunt. Cue to the pitchfork emporium / Twitter MC of the day.
upvote/like-based systems: people don’t upvote your content (increasing its visibility) because you’re right, they do it because you say it confidently.
on the Internet, nobody knows that you’re a dog: concern trolling made easy.
Now look at what @startle said: “Dunno man, seems like it might be the fascists.”. IMO that user is being spot on, those five things make social media specially easy to manipulate for fascists². And they’re mostly the ones creating this dichotomisation of society³, because that’s how they’re able to congregate the nutjobs into a political discourse. Suddenly the village idiot doesn’t simply say “they’re hiding aliens from us” (stupid, but morally OK), the discourse becomes “the Jews are hiding aliens from us” (stupid and Antisemitic).
By “assumers” I mean individuals who are quick to draw conclusions based on little to no reasoning, evidence, or thought. This plague exists since the dawn of time, it’s just that decontextualisation gives them more room to assume shit out of nowhere.
Fascists often babble about “virtue signalling”, without realising that themselves are prone to signal adherence to their stupid beliefs. They don’t want to be in the receiving end of their own witch hunts.
By “society” I mean at the very least Western Europe plus the Americas; probably more. It is not exclusive to USA.