There's only one God, VR. Though mankind through history has had a variety of names for the One God, even the Greeks, saddled as they were with the Olympian gods, understood that there could only be, at the end of the day, but one god -- for the Olympians were creatures (like men), although immortal. Therefore, the many gods of the Greeks and the other cosmological cultures of the past have their creative source in the One. And yes I'm pretty sure this would be the parsimonious hypothesis. FWIW, on the current state of my analysis. Best to you, VR -- good night and pleasant dreams. -- bb.
Many religions have disagreed, not just that of the ancient Greeks. If there aren't many examples around today, it's because some (at least two come to mind) of the later monotheistic religions have a history of expansionism and rabid aggression against the more laid-back polytheisms and anything else for that matter.
How does anyone know about this stuff? How does anyone kid themselves or anyone else that they know about this stuff? It's unobservable, untestable, and flat-out goofy.