If he did agree to destroy religion(I am ignorant on the subject myself), then I think the main reason he would do this is because he doesn't want a Christ, Yahweh, or some other deity getting in the way of his own domination. I would go so far as to say that he wanted to deify himself, at least in the minds of the people, and you can't do that when there are religions that claim there is only one god, and he is (fill in the blank)
"I trust my own reason and my own capacities to think and educate myself and to reach greater levels of knowlege and status through learning and work. To me, wishing for a god is like wishing to be a slave, it is like declaring that one is too incompetent to handle one's own affairs." - the germans are coming
