Islamic Persia was the Mongols' second great civilization to be invaded. The Mongol capture there was considerably more rapid than the lengthy conquest in China.
Prior to the Mongols, the most recent incursion had included Turkic peoples, but they were Muslims who had recently converted, were few in number, and solely wanted to be accepted inside the Islamic world. The Mongols, on the other hand, were considered unbelievers by Muslims, and their unexpected success came as a shock to those who had become accustomed to history being viewed as the steady spread of Islamic power.
When Hulegu's successors' Mongol kingdom fell apart in the 1330s due to a lack of a suitable heir, the Mongols were not expelled from Persia as they had been from China. They and their Turkic friends just vanished, absorbed into Persian culture.