What the hell happened to this subreddit?

I remember 2 years ago the posts on this subreddit were 50% left leaning and 50% right leaning. Then about a year ago it started becoming majority left wing whilst still making making posts that pointed out stupid/bad things from the left wing side of politics. But now after checking the subreddit recently. It's become completely 100% left wing. I guess I'm gonna answer my own question but my guess is over time every single person that's not a republican hating liberal has left the subreddit because any post or comment that's not on the left side of politics would just get downvoted. So over time more and more people leave until the only people left are the people of all the same opinion.