1. Hinduism is not Polytheism. It’s Henotheism, meaning each god is believed to be a window on the One or the All.
2. In Hinduism, “the physical realm doesn’t exist.”
The supreme reality is known as Brahman. The same god, if you can’t grasp the abstractness of infinite cosmos represented by an infinite being, can be encountered physically by Saguna Brahman, god-with-physical-attributes. This version of the deity is very close to the Jewish and Christian image of God as the loving Father. If nothing exist, how can there be Saguna Brahman, by your argument? Read more 10 Common Misconceptions about Buddhism and Hinduism and their Influences in the West