There are patterns of bot-posters, as well as the fact that in many cases the content exists elsewhere online and was copied.
You can’t really. While you can ban individual accounts, they are able to make more, as I’ve said before it’s very easy to evade bans in ways that prevent easy ban evasion detection on Reddit’s part. It’s also likely that if Reddit is doing it they won’t enforce ban evasion against bots, though I find that option less likely.
Two questions:
You’re not banning anything. Reddit runs the bots