Pet theory (disclaimer that I know very little about SEO) would be that the website with the cloned content loads fast and does not load 4 MiB of javascript, thus beating the original content in ranking mostly because of the speed, which is I believe a important factor in Google rankings (and getting more important).

And add to that the some link spam and preventing the visitors to return not get any bounce back...

Either way, I can't help to be a bit impressed by the SEO spammers outsmarting the people at Google. (Edit: and I don't mean to say they are smarter or anything, just that they only need to find one weakness in the algorithm while the people working to improve it needs to make it works for everything.)