The assumption of my scenario is that in our universe Israel, or more specifically the Kingdom of Judah, was not officially monotheistic prior to the Babylonian Exile which began in 586 BCE. This is to day that the god Yahweh (YHWH) was served alongside the goddess Asherah/Ashtoret. A few other deities may have been recognized as well, but when the Jews went to Babylon and as the Persians took over this all changed. A new temple was built in Jerusalem and, with Nehemia as governor over the province of Yehud (Judah) with Ezra as High Priest, Judaism emerged as a religion based on the belief in one god. References to other gods in the sacred texts which Ezra had stitched together to form the Torah were rationalized such that they conformed with monotheism. It's thought that Ezra may have been influenced by Persian Zoroastrianism but, whatever the origins of Jewish monotheism, it later had an influence on the development of Christianity and Islam. Thus, I propose a universe wherein the Persians do indeed conquer Babylon and do indeed allow Jews to return to Judah and rebuild the temple. However in this scenario the new Jewish leaders are no more monotheistic than had been their pre-exilic predecessors. They resore a religion in which Yahweh and Asherah continue to be worshipped side by side as the chief god and goddess of the Jews.