In what ways was the Buddhist theory of a social contract different from the Brahmanical view of society derived from the Purusha sukta?

This is what a famous historian of Indian literature, Maurice Winternitz, wrote about the Mahabharata:

“Just because the Mahabharata represents more of an entire literature . and contains so much and so many kinds of things, it gives us an insight into the most profound depths of the soul of the Indian folk.” Discuss.