The bigger the group of people, the more bad apples there are among them. It’s just statistics - plain and simple. Reddit is a huge platform, so there’s naturally going to be a great number of bad people there. Something to also keep in mind is the gap between how bad someone truly is and how bad you imagine them to be. We’re pretty quick to judge and label people, especially online, based on just a few lines of text. It’s highly unlikely that one’s assessment of someone’s personality as a whole, based on a handful of social media comments, is anywhere near an accurate representation of their actual views.

Also, these same extremists are just as present here on Lemmy - they just mostly fly under the radar because it’s a rather homogenous group of people from a political standpoint, and those extremist views therefore tend to align with your own.