tl;dr = Google at first approved of the tactic these guys used then suddenly without warning changed their search algorithm and penalized these guys. Lesson, don't rely solely on Google to build traffic or you might lose a lot of money. They lost $400k in business from it.
Google changes its search algorithms periodically in an attempt to thwart the SEO spammers, which sounds like a good thing until you notice a lot of sites which had good in-depth information - but wasn't really SEO'd much if at all - are unfortunately also disappearing from the results along with the spam. It could just be my nostalgia, but the Web felt like a much... richer place 10 years ago. Sure there was more spam (and it was relatively easy to ignore), but among that were sites which had lots of interesting info, in very simple and readable styling, and almost no ads. These days it seems Google second-guesses queries far too much, and all you get are bland-looking, very similar sites with very meagre portions of irrelevant or superficial information along with large amounts of (I block them, but some still slip through) ads, social media widgets, and other distracting cruft.
I guess that could be Google over-filtering, but I think the more likely explanation is that 10 years ago that there wasn't as much much SEO effort, so it was easier for Google to pick the good pages out. So if Google weren't aggressively trying to correct for SEO spam, you'd see even more bad sites with meager information and lots of social media widgets.