You are correct in saying that the Hebrew people embraced monotheism. The process is lost in history in terms of the details, as much of ancient history is. However, this limitation does not have to hinder a general historical understanding.
I would say that the most important developments in the develop of monotheism were the Torah and the temple. The laws of Moses, which the Hebrews consider to be inspired clearly called for a monotheistic religion. Moreover, there is active punishment when it comes to those who embrace polytheism. Think of the gold calf incident in the book of Exodus.
Second, temple worship, which was firmly established in the reign of king Solomon created a central location for worship. This one temple made the worship of one God clear. However, it must be stated that there were many times when the people lapsed into polytheism.