Most ancient societies were multi-faith, of a sort. Ancient pantheons were not nearly as exclusive as modern ones. To use an example from Egypt, prior to the unification of Upper and Lower Egypt, each region had its own lion-headed warrior goddess. The delta region had Bast, while Upper Egypt was devoted to Sekhmet. With the unification, both goddesses were slowly woven into the same pantheon, and Bast shifted from a lion-headed warrior to Bastet, a feline protector and something of a counterpart to her more aggressive "sister".

That is how most ancient societies operated. As long as the worship of any particular deity was not disruptive, ancient peoples tended to be unconcerned with which god you worshiped. After all, when you already have dozens of gods in your pantheon, what's one or two more?