Reddit develops it's own narratives, and those narratives end up being all that gets visibility (because of the comment upvote model). Ideas like 'all conservatives are MAGA losers, look at the idiots on /r/conservative', 'AOC and Bernie are God's gift to Earth' and 'minimum wage should be $45 and all student debt should be forgiven' are the only opinions upvoted. This directly leads to reactionary places like /r/The_Donald getting created. Then, when those communities get banned, it creates even more hostility and resentment. The best part of Donald Trump losing the election was that 80% of the front page wasn't articles shitting on him anymore.
I have to constantly remind myself that the people commenting on reddit are not an accurate representation of the real world, but I worry most people don't do that and legitimately believe people on the other side hate them. They react to this (inaccurate) belief with their own hostility and it becomes a self-fulfilling prophecy. If I had to put my conspiracy hat on - I think nurturing this hostility between ideologies would be the best way for a foreign power to destabilize the US; they're probably already doing it to some extent.
Honestly, I'd like to give it up entirely but it still remains one of the best resources of really useful, non-marketing knowledge on the internet.