Halcon: Why would he undermine himself by claiming someone was greater than man?
To offload responsibility? To assign himself an authority that he didn't earn? To grift as efficiently as possible?
Granted, the more likely explanation is that it began as a way to explain the (then) inexplicable. The development of gods into powerful invisible friends would come gradually, and the abuse of the concept would follow soon after, is my guess. The art of the con has existed about as long as human societies have.