Explain the historical circumstances that led to the expansion of the Mongol Empire. answer quick pls

In short, it was the growing resentment of the Mongols by the Chinese and surrounding states.

Explanation:

The Chinese continued to refer to the Mongols as barbarians, socially outcasting them to the point where the Mongols could not tolerate this outcasting, and began raiding villages on the outskirts of these states.

they were the direct result of some cultural difussion.

d. migration