How do the mytho-historical accounts of the Ancient Hebrews reflect the clash between monotheistic and polytheistic

How do the mytho-historical accounts of the Ancient Hebrews reflect the clash between monotheistic and polytheistic beliefs among them? Did monotheism come into existence fully formed and uncontested or did it have to coexist with polytheism for a long time? Focus on the narratives of Abraham in Ur/Mesopotamia and Moses at Mt. Sinai, as well as his reception by the Hebrews when he returned with the tablets. Make sure to include Yahweh and Baal in your explanation. What do these stories tell us about the religious beliefs and practices of the various peoples who lived in those regions during the Bronze and Iron Ages?  Related to this: should historians take these and similar mytho-historical accounts from different cultures and time periods uncritically at face value?  If not, how can we sort out “what actually happened” and at least begin to separate “history” from “mythology” in any systematic and methodical fashion?