Depends on the bot. There are many that go into subreddits and repost old popular posts. Sometimes in subreddits you wouldn’t think of. Like, for some reason the King Of The Hill subreddit had a really bad reposting bot infestation. I guess those wholesome and kind of niche but moderately active subs are chosen because people are less likely to dig into it, but if you check on the post history it becomes clear it’s an account with no comments that is just reposting content back into subs.