Religion is natural to mankind. It is one way we relate to the world around us. Nature and human experience have many aspects, so it natural for us to give these various aspects an identity and to seek a relationship with them. This natural human impulse is what created the pagan gods.
But why were these pagan gods, representatives of specific phenomena, overthrown in most of the world so that now, apart from animist religions among primitive peoples, paganism only exists in India and Japan as a higher level religion? Like a self-fulfilling prophecy, the success of the monotheistic religions seems to prove their truth to their believers.