The initial wave of users onto reddit clones often include a disproportionate amount of malcontents. A lot of people who don’t play well with others, who are banned from reddit (or at least banned from lots of subreddits) usually turn up first on these reddit alternatives and disrupt the community by repeatedly showing anti-social or disruptive, attention seeking behaviour. It’s not even necessarily related to any political persuasion. This stuff can collapse budding alternatives.

The first wave of new users on reddit alternatives are, in my experience, more likely to have a lot of problem users and since the sites are so small, and usually sparsely moderated, they are much more disruptive than they would be on reddit.

From what I can tell, the Fediverse has got past that.