I'm pretty sure most of those Reddit clones get flooded with "undesirable" bots as a way of killing them off. The people who currently run bots on Reddit, have massive power over public opinion etc, they want to keep their victims centralised, and on familiar territory.
Or, the majority of people are fine with limiting hatefullness and so you end up with just the people who want to spread hate online, which in turn makes it a cesspool
