In general, no, Mesopotamia did not fall because of attack from other empires, since it was primarily due to the Tigris and Euphrates Rivers drying up that led to a lack of produce, and therefore a fall in the empire itself.
Hinduism's worship many gods that are parts of a whole soul (Brahman). Buddhism's don't rely on gods but how to stop suffering by right thinking and self-denial so they only worship the Buddah "The Enlightened One."
I hope this helps you:)
