Why were Egyptians polytheistic?

Apart from a brief period of monotheism during the reign of Pharaoh Akhenaten, who ruled Egypt between 1353 and 1336 BCE, the ancient Egyptians were consistently polytheistic, as was almost every other culture in the ancient Near East. Only the Zoroastrian religion of the Iranian region was monotheistic until monotheism was adopted in Judah during the seventh century BCE.