Getting rich quickly is an evergreen topic because 1) we tend to link happiness to money and 2) we all like shortcuts. He is supplying a product to this demand.

Getting rich quickly is an evergreen topic because 1) we tend to link happiness to money and 2) we all like shortcuts. He is supplying a product to this demand. By spending money on advertisement, he increases the perceived value of his personality which leads to more book sales, more lectures (with higher fees), more YouTube views, etc. Basically, he's building brand awareness of himself, just like the Coca-Cola company does with its products.