They create an account and give it as human-like a history as possible (a few comments, enough time since registration that it doesn’t look brand new).
Then they sell it to whoever will buy it. This could be content marketers who want to promote a product, nation-states who want to influence Western voters, etc.
Mind you, I'm not claiming that's what's actually going on. But that could be the intent.
Then again I suppose the bots could also be upvoting, but I would assume that would be detectable to the voting ring detectors.
I don't know. Hacker News is supposed to be a place where human beings enjoy each other's company and conversation about common interests and intellectual pursuits but it seems like a lot of people here want to optimize the humanity out entirely.