It isn't just politics though or its why everything has to be shoved into one of two political platforms in the use (a few more in others) no matter how inconsistent or unrelated to the other planks assigned to that platform, take your pick.
People are wired to seek validation. What social media fundamentally does is connect a like-minded bunch of people however small a minority they might be, which lets them feel their wildest most disordered, anti-social thoughts actually enjoy some wide acceptance. They get their dopamine hit from someone agreeing with them, their brains cement their thinking along these lines because of that reward.
People used to try out their crank ideas on all their family, friends, colleagues, fellow congregants etc, and if they were unable to find any validation of them eventually let go and trained their brains on something 'acceptable'.
So society and many individuals can't discard any idea anymore no matter how stupid, disordered, dangerous, counter factual, etc it may be. Maybe this wider exchange of ideas means something notions, interests, theories, etc that are harmless or even good survive when in days past they would have either been extinguished or stayed in the domain of handfuls of cranks exchanging chain letters but it sure looks like the net effect is a lot of bad ideas and individual ideations get more oxygen because of social media than real innovative positives ones.