If 2/3 of US internet users are left of conservatives, that's why they get downvoted to hell anywhere outside their safe spaces. IMO the crazy moderators on reddit are a result of the left lean, not the cause.
Reddit leaned a lot more right/libertarian before nearly all coservative subreddits were systematically banned under spez and Pao. Spez also enacted more subtle censorship like algorithmic tweaks to keep t_d out off the front page and eventually the creation of /r/popular to keep similarly "undesirable" subreddits from the front page.
The truth means nothing to those that wont listen. The Republican party is a far right monstrosity. The democrats in US are a right leaning party for all practical purposes. Hell, Biden said he would be fine running with a Republican VP.