What is history: it is the echo of the past to the future, the reflection of the future on the past. - Hugo
As for why Sima Yan wanted to make the fool Sima Zheng the emperor, and did not have Sima You, the king of Qi, it must be carefully sorted out to have an intuitive understanding.
The Sima family was able to become strong during the Three Kingdoms period, mainly relying on Sima Yi, who supported the Cao family after being activated by Cao Cao, and later assisted Cao Pi, becoming an influential figure in the Cao clan regime, and in his later years launched the Gaopingling coup d'état, completely seizing the real power of cao Wei's regime, and the Sima family suddenly became prominent.
Sima Yi had two sons, the eldest son was Sima Shi and the second son was Sima Zhao, who was originally Sima Zhao's son, but because Sima Shi had no heirs, Sima Zhao passed him on to his eldest brother Sima Shi.
After Sima Yi's death, Sima Shi was in charge, but Sima Shi died young, and Sima You was relatively young, and in view of the special situation of the Sima family in the Cao Wei regime at that time, Sima Shi left the position of general to Sima Zhao on his deathbed so that he could continue to control the Cao Wei regime.
Sima Zhao's concubines, in addition to Sima You, also had Sima Yan, and in Sima Zhao's later years, he also faced a problem of choosing an heir, and according to the reason, there was no problem in passing the throne to Sima Yan, the eldest son of Sima Zhao, but the problem that appeared here was that everyone knew that Sima Yan's son Sima Zheng was a fool.
Many people are a little unfamiliar with the name Sima Zheng, in fact, Sima Zheng is still quite famous in history, as the second emperor of the Western Jin Dynasty, Emperor Hui of Jin, when the country was in a famine, the minister told the emperor that the people could not eat, Sima Zheng asked a question " The people are hungry without chestnut rice, why not eat meat?" ”
This means that if you can't eat rice, why don't you eat meat? Sima Zheng's words made him firmly recorded in the history books, accused of lacking a comprehensive understanding of things. Because of this, Sima Zhao did not want to pass the position to Sima Yan.
In Chinese history, there is no shortage of emperors who passed the throne to a certain son because of the excellence of their grandsons, such as Zhu Di originally liked the second son Zhu Gaoxu, did not like the eldest son Zhu Gaoxu, but Zhu Gaozi's son Zhu Zhanji was deeply liked by Zhu Di, Zhu Di finally passed the throne to Zhu Gaozi, and the most famous is probably the road of Kangxi's succession, Kangxi's sons are many, excellent is not in the minority, so there was a nine-son seizure incident, and finally Kangxi passed the throne to Yongzheng unexpected many people. There is a theory that because Kangxi liked Qianlong, he passed the throne to Yongzheng.
And Sima Zheng was really a "pit daddy" lord, because of his own stupidity, he almost made his father not inherit the great cause.
Sima Zhao did not want to establish Sima Yan, in addition to having a stupid son, but also because of Sima You, Sima You's identity is quite special, he was originally Sima Zhao's son, and then passed to Sima Shi, Sima Shi is the concubine of the Sima family, according to the ancient patriarchal system, Sima You even has more inherited power than Sima Zhao, in addition to the special status, Sima You's wisdom and Sima Zheng's stupidity are in stark contrast, Sima You was very smart when he was young, full of poetry, good at writing articles, very influential at that time, Sima Yi and his two fathers, Sima Shi and Sima Zhao, were also very optimistic about him.
When Sima Zhao succeeded Sima Shi's throne, he also said that after a hundred years, he would pass the throne to Sima You, and later Sima Zhao died strangely and violently, and many people speculated that Sima Yan was engaged in it.
In Sima Zhao's later years, he also broke his heart for the affairs of Sima Yan and Sima You, and often told their brothers the story of Cao Pi and Cao Zhi, hoping that their Sima family would not have such a "frying He too anxious" thing in the future, but after Sima Yan's body gradually deteriorated, due to the incompetence of the crown prince Sima Zheng, the people in the court hoped that Sima Yan could pass the throne to Sima You and bear the title of "returning to the country", for various reasons, Sima Yan finally planned to pass the throne to his son Sima Zheng.
In order to pave the way for Sima Zheng, Sima Yan asked Sima You to return to his fiefdom, when Sima You was still ill and vomited blood shortly after arriving in the fiefdom.
At that time, the eastern Jin dynasty scholars evaluated Sima Yan's gains and losses in power, believing that his mistake of establishing Sima Zheng without passing the throne to Sima You was the greatest, in their view, it was Sima Zheng's incompetence that caused the rebellion of the Eight Kings, and the Western Jin Dynasty was eventually seriously injured, and finally it was short-lived and destroyed.
In terms of the overall situation, sima yan was able to pass the throne to Sima You, and his great uncle Sima Shi passed the position to Sima Zhao for the sake of the family, not his own son Sima You.
Of course, people are selfish, everyone wants to pass it on to their sons, and in order to pave the way for their sons, they will not hesitate to kill the killer, in Sima Yan's time, there are many examples that can be learned.
After Sun Jian's death, Sun Ce established a firm foothold in Jiangdong, and was later assassinated, and when he was dying, he did not pass the position of lord of Jiangdong to his son, but to Sun Quan, which was also based on the overall situation, but Sun Quan called himself empress dowager, and did not even posthumously crown Sun Ce as emperor, but even suppressed Sun Ce's son, worried that his son would rob his son of the throne.
Sima Yan was probably also worried about where his position would be after passing the throne to Sima You, after a hundred years? According to the Zhaomu system at that time, he and his father's ancestral tombs could have been withdrawn from the Taimiao Temple, not to mention the stupid son.