I really need to go back and watch the whole thing, but I remember in one of the first two seasons there's another point where his wife discovers some duffel bags that he's stashed that are just absolutely stuffed with cash. Like, tens of thousands of dollars, if not a six-figure number. And when she confronts him about it (I think she knew what he was doing and he had promised to stop?), he says that he wants to make sure that she and the kids are taken care of after he dies.
But he was lying through his teeth. What started out as a desperate attempt to save his life quickly spirals into a power trip, and his ego can't let him stop even when he has no need to keep going. The money is just a side benefit at that point.