Dralel: Uh, thanks for the clarifications... :D
TL;DR version:
There was a Fall Insomnia Sale, which worked pretty much like this one, except
- free games were available directly from the front page, for split seconds, and
- GOG didn't anticipate the demand, the publicity and the enthusiasm.
Which is why cult classics (that had been on sale several times and most regulars should have had them) like Deus Ex and Theme Hospital sold within minutes no matter the quantity, and games which weren't cult classics and thus presented little interest for the HUGE irregular audience stuck around for exponentially longer.
Now, Jack Keane 2 happens to be a movie-like point-and-clicker made by a German company for the German market, where adventure games are
huge, fans of the genre keep buying and playing everything, and the price tags are comparable with those of AAA titles. As such, these games (Deponia, Satinav, Edna, Unwritten Tales, Whispered World and of course Jack Keane) are considered to be "kind of" to "significantly" overpriced on the global market. It's especially noticeable on GOG, where AAA releases are few and far between and there's much more playtime, depth and replayability to be found in a typical classic oldie.
So Jack Keane 2 is fairly unknown, happens to be a part 2 of a series, costs a lot, and the discount wasn't deep enough for greed/completionism to kick in - for the same price you could have bought a bunch of standalone well-publicized classics. And Jack was stuck on sale for a long, long time, so much that I went to sleep and didn't miss anything. At some point, people got the idea to rate the game 5 stars and add hilarious reviews, in a tongue-in-cheek effort to persuade more people to buy it. Other people loudly objected to the fake reviews because they thought they were destroying the integrity of the site's user feedback, still other people raged at GOG for using blackhat social engineering and taxing their minds and bodies for pitiful amounts of real dollars, yet others were bitter about never getting free games and blaming script kiddies / Eastern Europeans in general (even though GOG uses a content delivery network), there was 503, there were GOG Atlas bears, lags, bugs, rage, drama, sleep deprivation, and Jack Keane was in the center of it all.