I mean what do people do after learning they are fat and feel depressed? They buy crap to feel better. Maybe your website is exactly what advertisers need.
It is quite sad that anyone would consider this a business opportunity.
But yeah, that is a smart way to upsell. Even if it's morally questionable.
Google gives you the choice where you want your ads to be displayed; whether it's within the Google search results, or on websites like yours, or there are programs like Google Doubleclick where you can chose which websites you want to display your ads.
I think most of the criticism here doesn't so much reflect the ignorance of advertisers like the parent comment says, but ignorance of the people commenting how advertising works.
But are they? If they're paying per click, completely uninterested visitors won't cost them anything anyway. As dkuebric pointed out, we have no idea if those 395k sites were actually costing them any significant amount of money.
On the other hand this huge "fraud" is what makes Google free and has thus powered the information revolution that now looks like a pivotal turning point in human history. Hard to be all that mad that Google made all the worlds information freely searchable by ripping off dumb businesses...