During the Cao Wei period, the twenty-grade official system was officially abolished and replaced by the enfeoffment system. In fact, Cao Wei has existed in name only after the "Change of Gao Pingling", and the real power is in the hands of Sima Shi. At that time, Sima Shi wooed many gentry in order to gain political power better. It can also be said that Sima Shi's Jin regime was actually established with the support of the gentry. Therefore, in order to consolidate his political power, Sima Shi must win over the gentry. This economic and political advantage gradually leads to a new system-gate valve system.
Therefore, personally, it is reasonable to think that Sima Daigu's coronation ceremony is the imperial clan that has mastered the political power.
Of course, it's just a personal opinion, for reference only.