Religions of the desert image - Atheists, Agnostics, and Anti-theists of ModDB

That's like the most plausible explanations for thoses monotheistic religions.
Daily routine became traditions, traditions became rules, rules (to be respected more easily) became divine and so you'll fear the punition for your physical form and for your "soul".
We fools ourselves into believing divine rules from a man's habit thousand of years ago... humanity is so naive, that's funny and sad at the same time.