I think the main idea is that God wills health and wealth for his people and that faith, self-empowerment and donating to these churches will bring on the goods (and, with the Dominionist-inflected sects, power).

I'm acquainted with some Christians who more or less subscribe to the Prosperity Gospel, and I'm scandalized by it. It's obviously a vehicle for bad actors to soak the credulous struggling for security and dignity in a capitalist economy, and, of course, its overriding values are not of the Gospel.