All writers of the Chaldaean period associate monotheism in the closest way with unity of worship.
Monotheism makes me grouchy. I don't trust any religion that makes God look like one of the ruling class. I guess I'm a pagan or an animist.
The deepest difference between religions is not that between polytheism and monotheism.
Islam, the third in historical sequence of the ethical monotheistic religions of the Near East, was very successful in establishing its monotheism, but had only very moderate success in spreading its version of Jewish and Christian ethics to the Arabs.
It's very clear from Biblical history and Jewish history that Jewish monotheism wasn't developed in an instant, that it became gradually the accepted norm. But undoubtedly, Jewish ancestors were polytheists.
There is a danger in monotheism, and it's called idolatry. And we know the prophets of Israel were very, very concerned about idolatry, the worship of a human expression of the divine.