According to historical records, Cao Cao died of illness, so it was judged that Cao Cao probably died of a headache. According to legend, Cao Cao had a headache because of overwork in handling affairs, so he turned to Hua Tuo for help. Every time Cao Cao had a head wind attack, Hua Tuo used acupuncture to help him stop the pain, but it could only relieve the pain for a while and could not cure it. Cao Cao asked Hua tuo to cure the wind. Hua tuo said he had to have a craniotomy. Cao Cao thought Hua Tuo was going to kill him, so he killed Hua Tuo. Cao Cao's suspicious character undoubtedly aggravated his anxiety.
However, the tomb of Cao Cao unearthed in Henan seems to have overturned this speculation: in fact, Cao Cao's death was similar to Zhuge Liang's, and both died of exhaustion. Zhuge Liang was not sick before his death, but he was overworked and worried about the incompetence of Shu Han after his death. He was worried all day long and eventually died of depression. Cao Cao is similar to Zhuge Liang. Cao Cao spent his whole life in depression. He wants to be king on his own, but he is afraid that he will not succeed. Therefore, he has been holding the emperor as a vassal and never claimed to be the emperor all his life. Maybe this is his heart.
No matter how Cao Cao died, he was not as cunning and treacherous as described in the novel. In fact, Cao Cao is much better than Liu Bei. Liu Bei is a hypocrite and Cao Cao is a real villain. He deserves to be a lean man.