Right? And who clicks the popups? I have no clue about the economics of online ads, but my understanding is, it is cents per click. This would mean hundreds of thousands visits per year? Sounds like there are bots involved to me.

There are loads of dead links hovering around on the internet, no doubt plenty of people (and bots convincing enough that advertisers still pay out) will accidentally end up on one of these domains, sigh at the annoying ad that interrupted what they were doing, and never return.