In fact, many people want to know why Cao Cao didn't just replace him. Actually, there is a reason. Every usurper in history rebelled because of the king's incompetence. In contrast, Emperor Gaozu didn't make any mistakes, so this result was obtained. Even if the usurper succeeded, he lost the hearts of the people. Second, Emperor Xian of the Han Dynasty knew Cao Cao's intentions, and since he did no harm to himself, he could still govern the country, so he was willing to be a puppet. The third is that Zhou left less land at that time, including military capabilities. If other vassal States rebel at this time, they will certainly take the opportunity to attack Cao Cao. Even if he wins the throne, he is incapable of fighting. To sum up, Cao Cao finally chose to support the emperor and set up a minister instead of rebelling.
And the reason why we did it, as you can see. That's how Cao Cao wanted to seize power, so that what he wanted to do was what Emperor Xian of Han wanted to do. If other vassal States don't do it, it's rebellion. At this time, he is active, and there will certainly be no other vassal States that can't do well.
In fact, I think that no matter what happens in the end, Cao Cao is really smart and has his own strategies and ideas.