Duke Hou Cao Jie could not solely oversee Xia Territory, and for considerable reasons.
Firstly, due to his military prowess and Yan Dao's cultivation, he easily raised Chuguo's vigilance. With Cao Jie overseeing Xia Territory, the surrounding areas would be uneasy. Secondly, his immense reputation from defeating Xia in a single battle makes it easy to form a separate regime.
In "Travels and Discourses," it is said, "Jade should not be placed in easily shattered places, how could a name lightly be granted to one who holds a vessel!"
The inherent rationale has been thoroughly explained.
This has nothing to do with whether Cao Jie is loyal or whether Emperor Qi trusts him.
It is an issue any emperor should avoid, avoiding giving a subject unwarranted space.
The Governor of Xia Territory is not Zhongxuan Chuliang, nor Li Zhengyan, nor Chen Zeqing, same principle applies.
