I think I can posit a reason, as I knew someone who read The Game and followed through on it. He was one part douchecanoe, one part dumb and two parts lonely. After reading it he became the jerk that one can reasonably expect. Which, in his case, meant that he appeared to be more assertive and confident while also acting like more of a dick. So he had some success with it. My guess is that the being-a-jerk part did nothing while the confidence-can-be-faked part did all the heavy lifting. He went on to preach about it to other guys - "hey, look at all the girls I'm talking to now". Granted, this was a few years ago, before /r/theredpill was even a thing. I still think word of mouth from close friends is how ideas like this spread. If I see a guy friend of mine suddenly doing well dating and he says he holds the key to success, I might be inclined to believe him.