Remember the Old Testament was the Judaic part. Which provided the tribal god of Judaism as the grain of sand at the center of the pearl, of the more universalist, aka globalist Christianity of the New Testament.
To the tribe, the Commandments are for the members only. The Romans adopted Christianity for its monotheism, around the time the Empire was rising from the ashes of the Republic. The Big Guy Rules.
Democracy and republicanism originated in pantheistic cultures. The family as godhead. To the Ancients, monotheism equated with monoculture. One people, one rule one god.
When the West went back to more broad based political systems, it required the separation of church and state, culture and civics.
Here is an interesting book on the origins of Western civilization and culture;
