reddit is an echo chamber when it comes to most topics, and politics are probably the worst of all. Back in the Gamergate days it was all MRA types (throwback!); in 2016 it became 50% Bernie and 50% Trump; these days it's mostly mainstream liberal. I assume the actual political makeup of the user base hasn't changed that much in that time, but people who obsessively refresh and upvote/downvote posts based on their politics have an outsize impact on what comes to the top. I'm sure there's some impact from automated astroturfing, but humans drive it.

No serious person would ever suggest using it to take the "political temperature" of society at large. It's about as useful as Nextdoor for that.