Tell me if I've got this right: Say you have some businesses in industry X that all rely on advertising. Say one of those businesses also happens to own the dominant advertising platform that businesses in industry X need to use, in order to effectively find customers. (Special note for those subset of HN readers who tend not to read: Yes there may be other platforms, but before you present that as an objection, note…
You are assuming that running and advertising business is profitable. If this is the case then yes, running an advertising business plus X always gives you an advantage over just doing X. This is true no matter what X is, even if X is unrelated to advertising, or even just doing nothing. I’m not sure in what sense this means that the game is rigged (unless of course the bidding process is unfair).
You are talking about a different aspect of the scenario, where the company is reaping profits from advertising. Sure, that's kind of beside the point though. Which is why it's important to recognize that the harm happens even without the advertising being profitable.