In the middle of the 17th century, the peasant rebel leader Zhang Xianzhong (1606–1646) from Yan'an, Shanxi Province, nicknamed Yellow Tiger, led his peasant troop from north China to the south, and conquered Sichuan. Upon capturing it, he declared himself emperor of the Daxi Dynasty (大西王朝). In response to the resistance from local elites, he massacred a large native population. As a result of the massacre as well as years of turmoil during the Ming-Qing transition, the population of Sichuan fell sharply, requiring a massive resettlement of people from the neighboring Huguang Province (modern Hubei and Hunan) and other provinces during the Qing dynasty.

Answer this question, if possible (if impossible, reply "unanswerable"): Why did the population of Yellow Tiger fall?
unanswerable