As an Internet Marketer, I'm gonna tell you what's happening....
When you make a certain number of youtube videos and they gain a certain amount of attention, youtube makes you a partner and they pay you. I'm not sure if dude is selling books or videos, but if he is, then Youtube is definitely a way to promote them. It's the same thing that Alex Jones is doing, except that Alex Jones has more money to spend....so he has his own radio show and doesn't depend on youtube. The process is simple: You play on people's fears, tease them with a so-called "solution," then tell them you have the solution (your book or video). That's it. That's why you see so many conspiracy videos on YouTube and other sites, because it's a hot niche that makes a lot of money, especially on the internet.