One is the loss of Wu Sangui's support.

Li Zicheng led hundreds of thousands of Dashun troops into Beijing, causing Emperor Chongzhen to hang himself in Jingshan Park of the Forbidden City. However, after forcing Emperor Chongzhen to death, Li Zicheng did not treat the people well, connived at his men burning, killing and looting in the city, and even occupied Wu Sangui's wife Chen Yuanyuan. At that time, Wu Sangui held the most elite army of the Ming Dynasty-Kanto fighters, which directly ruined Li Zicheng's chance to seize the world. Wu Sangui was furious when he heard that his wife was occupied by Li Zicheng. He opened Shanhaiguan directly and let hundreds of soldiers of the Eight Banners of the Qing army come in to join forces with the Qing army to attack Li Zicheng. The two sides fought with one stone, hundreds of thousands of Dashun troops were wiped out, and Li Zicheng was defeated and died. It's a pity that Li Zicheng robbed Chen Yuanyuan and ruined the best chance to win the world.

Second, Li Zicheng has lost popular support.

At the beginning of the Li Zicheng Uprising, the slogan "No food" was used, which was not wrong with Qiu Min, so many people supported Li Zicheng. Li Zicheng's team grew gradually, but Li Zicheng burned, killed, looted and robbed cloth in the later period. Therefore, after losing the popular support, Li Zicheng became addicted to debauchery gradually, so many subordinates were also chilling. In the end, Li Zicheng was defeated and fell short.

Third, the limitations of the peasant class in Li Zicheng.

Most of Dashun Army led by Li Zicheng are farmers. He is also a farmer's mind and doesn't know how to govern the country. Moreover, the fighting capacity of his army is not as strong as that of the Qing army. Before the Qing army entered the customs, it was an army on horseback, all of which were brave and good at fighting, and one was ten. Li Zicheng just wanted to separate one side, but he didn't have the courage and strength to fight to the death with the Qing army. Therefore, when Li Zicheng's army met the Qing army, it collapsed at the touch of a button, which was the root cause of farmers' restriction in Li Zicheng Thought. He doesn't know how to win the support of literati and people, nor how to manage the army.

To sum up: Li Zicheng was wiped out for the above three reasons.