I know. I didn't say the ads were ranked for highest bidder. I said they were ranked to maximize profitability. If the user does not click an ad, it's not profi

I know. I didn't say the ads were ranked for highest bidder. I said they were ranked to maximize profitability. If the user does not click an ad, it's not profitable to Google. If the user comes back to the search page after visiting the ad, the ad is not profitable to the advertiser. But if the user buys from the ad, that doesn't say anything about whether the ad was useful (or counter-productive) to the user, it only means that this transaction was profitable to Google and the advertiser. Ads not matching the search query are not the issue. They are neither profitable nor helpful, so you can't use that criterion to distinguish the two goals.