Why are people so rude on Reddit compared to the Fediverse?

I notice this especially with my Norwegian learning. People are rude, call me names, or make fun of me on Reddit for using the wrong word or "en" v…

I think it has to do with community size. Even on reddit, the smaller and more insular communities are much more pleasant than the frontpage ones.
This has been my experience. Plenty if small subreddits I’ve perused where when they were small, they’re all politle (whether in humor, serious discussion, or sharing hobbies). In time as they grew it just brings in more and more uh, typical redditors. Thats when you knew either abandon ship and make /r/true[subject] or just cut it out.