Multiple Gods?

If I'm being honest I think its weird that the Legendary Birds are getting Galarian forms, I don't hate it I just find it weird. Why do gods need to evolve into new forms to adapt? Their gods, they're already too powerful they don't need to adapt they're perfect. I also think its weird that there's more then 1 of the same god.

I don't remember if the birds had any established lore. So I assumed they were just extraordinarily rare pokemon, not gods.

In the 2nd Pokemon Movie they had lore. Disturbing all 3 they would fight endlessly until the world is destroyed