>>/41928/
Great question.
You see, Yahweh's power does not come from the faith of his followers, but from the number of occasions when his laws were circumvented in some clever way. This is why he created 613 commandments all of which inconveniences the life of his people so much that they are forced to find the loopholes in the commandments. They bending his rules for thousands of years now, day in day out, this made him very strong.
The topic reminds me of M.A.G.U.S. the Hungarian role playing game I wrote about here >>/12621/
The fictive philosophers and theologians of Ynev - where the existence of gods is a fact - came up with many ideas where the gods' power originates. One idea is the "parasitic gods theory" which assumes that the Gods live off from the worship of their followers.