LOL, Not a Captive, Lewis Black, a Jewish comedian says "of course God had to tell the Jews how to do everything, even how to get married. They were three hairs from a baboon!"
It's pretty much what you're saying...the Bronze Age was one of the most awful and violent times in human history. As awful as we may think the people of those times behaved, the Mosaic law (and other law codes, the somewhat similar Law of Hammarubi for those other Semites, the Chaldeans) was definitely a civilizing aspect.
To modern humans, harsh and demanding, but to those people, probably a lot more civil that whatever was previously held to. We know that Abraham came from the Chaldean city of Ur...and the bare beginnings of what we call civilization began there. Writing, codifying law, the beginning of people settling into cities around were agriculture now allowed for feeding such larger populations,placing themselves under law and the command of a central authority for protection all gave people the time and ability to do these things in a way the nomadic life hadn't always.
People like Abraham no doubt carried new ideas and civilization along with them, including the idea of one God, something that crops up every so often in human history in various forms. This time, it kind of stuck in a culture more than some others. However, not long after this the Persians developed their own monotheistic concept, Zoroastrianism. It may have been the latest thing in Gods at the time, to believe in one rather than many.
(I'm ommitting supernatural explanations, which are totally up to the individual to believe or not.)
But, much more violent and "earthy" times than we live in now, especially in the first world.