The Instability of the Indus Valley

By about 400 b c, you could see a great deal of commonality among these different societies all around the ganges plain and the himalayas. These non violent philosophies gained a lot of widespread influence even in places where they were not widely adopted or didn't displace vadic hinduism. But there also was a necessary instability. The balance of power among these mahaganapidas could not stay in place eternally. Eventually one state would be able to press some advantage, whether it was in wealth or population, and start to overcome smaller neighbors sand then further exploit that advantage until the balance of power fell apart.