Smoke
Done here.
Children have a natural propensity to believe all kinds of crap. They freely infer sentience in inanimate objects and, as Sunstone said, ascribe agency to events. If you exploit this weakness by filling their little heads with theism, then of course they'll become theists. That doesn't mean theism is hardwired into us, although it does mean we have a tendency to mythologize and imagine.
If we were to totally destroy all society except young children, they'd create religion right off the bat. Why do humans have an inherent need for religion and to know the divine?