People tend to be assholes. The more people in one place, the lower the chance of nobody being an asshole, and it does usually only take one. Then you add the karma system, which causes people to perform for the internet points. It’s not just people being a natural asshole for any number of reasons: people also reward the wrong things such as asshole behavior, Redditsplaining, zingers and stupid cringeworthy clichés. The karma factor is lower here, but still a thing.