If you read the old testament in particular, god never denies the existence of other gods, only that he’s the best one. Yahweh was actually just one god in an ancient pre Jewish pantheon. He was like Dionysus, a god of harvest and wine and rebirth. Different tribes had different chief gods, but all accepted the existence of the others. Just happened over time that the people who worshipped Yahweh were the only ones left and it became a monotheistic religion.

I’m sure back in the day, those gods were more similar to Greek gods, flawed and monstrous, and entities to fear. That’s why the old testament god is such a psychopath.