I know you're not referencing Hinduism specifically, but I think it's important to point out that Hinduism started out as polytheistic, as seen early on in the Rigveda, where they just assigned gods to everything that existed in nature, but as time went on it has become more monotheistic as generally accepted religous philosophy (AFAIK) says all these gods are merely expression of one true God.
So while the polytheistic cultural and worship traditions are kept alive, it's not 100% accurate to describe Hinduism as polytheistic. Panentheism is probably a better term to encapsulate it, but polytheistic and atheistic interpretations are not unheard of.
Why did Hinduism go from polytheism to more monotheistic teachings, as the world in general did? I have no idea. Sorry! I read a totally unsupported claim somewhere else that it might be because people are lazy as hell and monotheism is "easier".
Did you mean henotheistic, by chance?
No. He did not.
He's talking about how some Hindus believe Brahman, the universal spirit, is the only real god. Other gods like Vishnu and Ganesha do not actually exist, they are merely symbolic of/metaphors for Brahman. Or possibly they exist but only as aspects of Brahman, in which case that could still be argued as a form of monotheism, at least as much as belief in the Christian Trinity is monotheism.
It's my understanding though that such belief is mostly prevalent among Western oriented Hindu apologists, who are embarrassed by traditional Hinduism. Really, most Indian Hindus are totally polytheists. Although I suppose you might call many of these traditional Hindu polytheists as henotheists. Although the vast majority of polytheists throughout history have likely been henotheists.
