I think there are multiple reasons, but one I want to highlight is Reddit’s shift towards driving engagement at all costs.
I used the “new” Reddit for a while, and I noticed that more and more it was trying to recommend posts and communities to me. “Popular with users in your area,” “Similar to another community you visited,” “You visited this community before”. A lot of the time, these would be posts and communities that I didn’t like or want on my feed.
I would venture to guess that these recommendations are putting people into contact with communities they wouldn’t normally seek out, and since they’re not a member of that community (and may even be hostile towards it), you get more people breaking community norms or trolling or antagonizing people, etc…
Someone should make a site where everyone can post their shreds and we can see things like total karma burned or total comments shredded, or top shredded accounts.