Sima Yi was able to successfully seize power through Gaopingling because of the weakness of the Cao clan and the strengthening of the shi clan's power, and second, because Cao Shuang was too wasteful.
The strengthening of the strength of the Shi clan and the weakening of the Cao royal family were important reasons for Sima Yi's success During the Eastern Han Dynasty, the Shi clan had great power. Not only did they control a large number of land populations, but they also relied on the relationship between protégés and former officials to influence government and local affairs. After Cao Cao raised the army, because he was not born tall, the relationship with the warrior clan was not too good, so the relationship between the two sides was stiff. It was only because Cao Cao's military strength was so strong that the shi clan had to submit to orders.
After Cao Cao's death, Cao Pi began to ease relations with the Shi clan. He also implemented Chen Qun's Nine Pins Zhongzheng system, so that the shi clan could make others stand out through the opportunity to recommend the sages. Since then, the power of the warrior clan has grown day by day, and its power has become increasingly powerful.
On the other hand, perhaps because Cao Zhi and himself were fighting for the right to inherit, Cao Pi was very wary of the imperial family, stipulating that "princes must not interfere in politics." As a result, the concubines of the Cao clan were excluded from the center of power. Only the collateral royal families such as Cao Ren, Cao Hong, Cao Xiu, Cao Zhen, and xiahou were still active in the court.
With the death of Cao Ren and others, the two major royal families of cao and xiahou were in decline and were unable to compete with the shi clan. To make matters worse, both Cao Pi and Cao Rui died young, and the imperial power that could have restrained the shi clan was weakened.
When Cao Rui was seriously ill, he originally intended to appoint Cao Yu the Prince of Yan, the leading general Xiahou Xian, the Wuwei general Cao Shuang, the Tun Riding Colonel Cao Zhao, and the Xiao Riding General Qin Lang as ministers. Most of these people were members of the Cao and Xiahou clans, and Qin Lang was Cao Cao's adopted righteous son, so all of them were members of the imperial family.
"Spring and Autumn of the Han Dynasty": The emperor made Wang Yu of Yan a major general, and made him an assistant to the leading general Xiahou Xian, the Wuwei general Cao Shuang, the Tun Riding Colonel Cao Zhao, and the Xiao riding general Qin Lang. This appointment was fully opposed by the ministers of the Imperial Sergeant Clan, and Cao Rui's close and trusted ministers Liu Fang and Sun Zi also expressed their opposition because they were at odds with Xiahou Xian and others. In this case, Cao Rui could only serve as a minister of gu order together with Cao Shuang and Sima Yi, the most senior minister among the warriors. Cao Yu and others were expelled from the center, and the imperial family's strength was weakened again.
Cao Shuang's incompetence caused almost all of his ministers to fall to Sima Yi's side, and after Cao Rui's death, Cao Fang succeeded to the throne. At this time, although the Shi clan already occupied an absolute advantage in the court, it did not pose a fatal threat to Cao Wei.
The gentry were concerned only with the interests of their own families, so they were not monolithic. Sima Yi was able to serve as a minister of gu orders only because he was elected because he was the most senior among the ministers from the shi clan, and it was not that he could influence the strength of other clans. After all, Cao Wei had also established a considerable amount of time, and some ministers in the court also had the heart to be loyal to Cao Wei, so there was not much crisis for Cao Wei at this time. Even Sima Yi did not have any intention of usurping the throne.
However, Cao Shuang was bent on fighting with Sima Yi for power. In the early days, he did push Sima Yi out of the center of power. However, Cao Shuang's ability was too poor, and the war he launched against Shu ended in failure, with heavy losses and a great loss of Wei's national strength. Moreover, Cao Shuang wantonly appointed his own cronies He Yan, Deng Biao, Li Sheng, Ding Mi, and others, and he was slow to return the government to Cao Fang and exclude Empress Guo, which caused dissatisfaction among other ministers.
Therefore, when Sima Yi launched the Gaopingling Rebellion later, Empress Guo and most of the ministers sided with Sima Yi. Even the ministers loyal to Cao Wei thought that Sima Yi's move was a reversal of the chaos and supported it in favor of the State of Wei. These people all played different roles in the coup.
Empress Guo's edicts provided a great basis for the legitimacy of Sima Yi's coup. The lieutenant Jiang Ji took advantage of his many years of service in the Chinese army, and together with Situ Gaorou and The Servant Wang Guan, he assisted Sima Yi in controlling the Chinese army and mastering the main force of Luoyang.
In contrast, there were very few ministers who supported Cao Shuang, and only one of them had weight. Therefore, it can also be said that Cao Shuang himself pushed most of the people to Sima Yi.
Therefore, Cao Shuang did not lose to Sima Yi alone, but almost all the ministers of the Wei central government opposed him together. It was not until Sima Yi overthrew Cao Shuang's dictatorship that some people were either loyal to Cao Wei or dissatisfied with the sima family's dictatorship and tried to resist. However, because the Sima family controlled the central power, these rebellions ended in failure. Cao Wei's fate was irreversible.