Organically grown niche communities don't deliver quarterly growth numbers, so Reddit has put no effort into any sort of guardrails against hostile takeovers by astroturfing content farmers. The logic of the attackers doesn't go beyond "this subreddit has a lot of subs and we have methods of dumping the mod team and turning all new posts into content slop that generates revenue for us". Stuff like this is just the choking gurgles of a dying platform.