Just as in the real history, why did Emperor Gaozong of Qi not actually need to worry about Emperor Yingzong threatening his throne?
Because according to the thinking of normal people, General Han Fuyue, the bulwark of the nation, was promoted by Emperor Gaozong himself and was his confidant. As long as Emperor Gaozong kept General Han Fuyue, and with General Han Fuyue's command over the military to support him, then Emperor Yingzong wouldn't even dream of usurping the throne—even after the death of Emperor Gaozong, when Emperor Xiaozong ascended, Emperor Yingzong would still have no chance.
Not to mention that General Han Fuyue was not the only powerful minister under Emperor Gaozong.
It could be said that the vast majority of ministers in the court supported Emperor Gaozong. In such circumstances, with no one to collaborate with, how could Emperor Yingzong stage a coup?
But the situation was different now.
General Han Fuyue was nearly driven to rebellion by Emperor Gaozong.