It used to be NYC for how much withe's
Answer:
Diseases that they were never exposed to, such as smallpox, killed close to 90% of the population. With most of the opposition to the domination gone, the Spanish could easily sweep in and conquer who was left.
Explanation:
Under Kublai Khan the Mongol empire reached its largest extension. He ruled over 24000000 km² (nearly 10000000 mi²). The empire went from China and Korea to Iran and southern Russia, from the Korean peninsula to the Danube River.
During Kublai's reign the empire was divided into four smaller Kanatos but he still remained as the Great Khan of all of them. He was actually the first Khan to successfully conquest China in 1279, making him the first Yuan ruler of the whole China. After his death, the mongols didn't elect a new Khan and the Kanatos became more independent.