1. The ruling foundation is weak. Sima family started as a civil servant of Wei, far less than Cao Cao who started as a warlord. Power comes from interpersonal networks and all kinds of intrigue, so the control over others who are also Chen Wei is far from as powerful as imagined. After the efforts of three generations, Sima family finally completed the change of Wei and Jin Dynasties. The Sima family did not firmly control the outstanding generals on the border and did not realize military centralization.

2. The mistake of choosing a successor. After Sima Yan proclaimed himself emperor, he insisted that his idiot son Sima Zhong be the crown prince, and refused to let his wise brother inherit his throne, which led to his opposition to Manchu civil servants. Sima Yan had to demote several ministers, and introduced his wife Sima Zhong's mother and Yang Guifei's family into the power center, which further aggravated the civil-military dispute in the Qing Dynasty.

3. The decline of Sima family and its becoming an independent warlord. At the beginning of Jin Dynasty, the indulgence and neglect of management of Sima family led to its decline. After Sima You died, the Yang family became bigger. At this moment, Sima Yan was worried that his idiot son would make the same mistake as Cao Wei, so he widely spread the kings of Sima family as vassals, increased the territory and actually led the troops, and stopped the armed forces in counties and counties at the same time, so almost all the kings of Sima family became vassals who could support their troops and respect themselves.

The emperor was incompetent and the queen usurped power. After Sima Yan's death, Sima Zhong, an idiot, obviously couldn't control the situation. Yang Guifei's family was immediately killed by Jia Design, the queen of Sima Zhong, which opened the situation that the queen listened to politics. Later, the queen killed the prince Sima Yu, who was not her own, which led many princes in Sima's family to rebel and killed Queen Jia, thus opening the famous Eight Kings Rebellion.

5. Jia is authoritarian in governing the country, and civil strife is everywhere. After Sima Yan's death, Sima Zhong, an idiot, couldn't control all this. After Sima Yan's death, Jia, the empress of Sima Zhong, staged a coup, killing Sima Lianghe, and the power base established for Sima Zhong collapsed instantly. After relying on the emperor to establish a prince, the national government gave Zhang Hua, the powerful minister, political stability for several years. Then, because Empress Jia abolished the killing of Prince Sima Yu, Sima Lun, the king of Zhao, rebelled, killed Empress Jia and Zhang Hua, and started the Eight Kings Rebellion, and even the Five Hundred Years Rebellion in China.

Extended data:

The Jin Dynasty (266-420) was divided into two periods: the Western Jin Dynasty and the Eastern Jin Dynasty, in which the Western Jin Dynasty was one of the unified dynasties in China history and the Eastern Jin Dynasty was one of the six dynasties. Fifteen emperors were spread in the Jin Dynasty, 155.

In 266, he usurped Wei, established Luoyang as its capital, and gained the title of Gold. Historically known as the Western Jin Dynasty, Wu was destroyed in 280 and unified. After the Eight Kings Rebellion and Yongjia Disaster, the national situation gradually declined. In 3 16, the western Jin dynasty was destroyed by barbarians in the north, and there was chaos in the north, which was called five chaos in history. In 3 17, Jinshi moved south, and Si Marui established the Eastern Jin Dynasty under Jianye, which made many northern expeditions. In 383, the Eastern Jin Dynasty was temporarily consolidated after the war with the former Qin Dynasty. During the Jin Dynasty, Wuhu moved to the Central Plains, strengthened ethnic integration, and northerners moved south to develop the Jiangnan area. In 420, Liu Yu established Liu Song, and the Eastern Jin Dynasty perished. The history of China entered the Southern and Northern Dynasties. ?

The Western Jin Dynasty inherited the territory of Cao Wei, and after reunification, it occupied the territory of Sun Wu. The eastern Jin Dynasty increased and decreased with the change of territory, and the northern boundary was mainly in the Qinling Mountains and Huaihe River.

The political system of the Jin Dynasty was clan politics, which was the basis of the six-part system in the three provinces of Sui and Tang Dynasties. ? Compared with the Three Kingdoms period, agriculture, commerce and handicrafts in the Jin Dynasty developed further.

Although the Jin Dynasty was the declining period of China culture since the end of Han Dynasty, it made new progress in philosophy, literature, art, history, science and technology. Jin Dynasty culture is developing towards diversification, which is an era of cultural creation, conflict and integration. Because the exclusive position of Confucianism has been broken, philosophy, literature, art, history and science and technology have been innovated, and some of them have become independent knowledge. Contemporary ideas, including metaphysics, Taoism and Buddhism, spread from India to the East, and scholars gained the upper hand by talking openly. Because the frontier nationalities brought grassland culture, the Eastern Jin Dynasty had the Central Plains culture and Jiangnan culture, and the two sides gradually began cultural exchanges or ethnic integration.

Reference link: Jin Dynasty (Chinese historical dynasty)-Baidu Encyclopedia