When Sima Yi proclaimed himself emperor, the Western Jin Dynasty briefly became the most powerful country among the Three Kingdoms, so Sima Yi's descendants could destroy the Three Kingdoms. The reason why the Western Jin Dynasty only existed for a short time in history is also because the descendants of Sima Yi were not harmonious.
The specific reasons leading to the demise of the Western Jin Dynasty are as follows:
The first thing: let the mentally retarded be the emperor. This emperor is the bad king written in China's book. His famous saying is "Why not eat minced meat?" How did such an emperor govern a country well?
The second thing: let incompetent people take charge of state affairs. "Don't think about the country, think about yourself." This was the courtier of the Western Jin Dynasty at that time. At that time, the courtier of the Western Jin Dynasty was also ridiculed by the people: irresponsible.
The third thing: Let the queen run the state affairs in disorder, Jin Huidi is mentally retarded, but his wife, Jia Nanfeng, is smart and capable, taking advantage of Jin Huidi's mental retardation to control the state affairs for a long time, and Jia Nanfeng is cronyism, making a mess of the Western Jin Dynasty.
The fourth thing: After the death of Queen Jia Nanfeng, the whole Western Jin Dynasty was completely out of order. There were eight princes fighting with each other in the imperial clan of the Western Jin Dynasty, which was called "Eight Kings Rebellion" in history.
The above four things led to the demise of the Western Jin Dynasty. These four things complement each other, and not only one thing led to the demise of the Western Jin Dynasty.