Potentially ny mass genocide. It is esimated that around 30 million people were killed under the rule of the Mongol Empire, and the population of China fell by half in fifty years of Mongol rule.
China was made up of seperate feudal kingdoms and many also suffered the humiliation of having to acknowledge the Jin Dynasty as formal overlords. Perhaps had they unuted in a joint cause they might have been able to resist the Mongols.
The Mongols used intimidation tactics, military hardness and dominance - particularly out of season when people were resting during winter. The system of government was more or less a meritocracy, and this encouraged expansion, power, wealth and merciless brute force.