So, reading up on the history of the Three Kingdoms period, one of the main reasons the Sima clan overthrew the Caos and established the Jin dynasty were the power plays between the regents of Cao Fang after the untimely death of Cao Rui, who were Cao Shuang, Empress Dowager Guo, and Sima Yi. In the chaos, Sima Yi and his sons eventually triumphed with the help of the aristocratic families.
Cao Rui continued the meritocratic practices of his father and grandfather before him, while the Sima clan seems to have based its power in the leading families. What if Cao Rui had lived to see his adopted son to maturity?