Because Troy Davis, in his tweet, literally said "I didn't know that black-hat content marketing existed"
I think his comments here indicate that what he meant was he wasn't aware it exists "at scale" in this way, but taking the content of the linked post at face value, it's easy to come away thinking "How did he now know this existed?". It's precisely what I thought after reading his tweets, but before seeing his detailed comments here.
Maybe he is a bot creator (or a bot account) that tries to discredit the importance of other bot accounts? I mean it would be the natural step for those groups to try to persuade the public (e.g. reddit users) that is not a big deal that those accounts exist.
What makes you think upvotes imply people don’t know this sort of thing exists?