There are actually two reasons. The first reason is that one mountain can't accommodate two tigers. In Romance of the Three Kingdoms, Sun Quan and Liu Bei made a temporary alliance to deal with the powerful Cao Cao army. Zhou Yu and Zhuge Liang, the first counselors around them, naturally became the counselors of this alliance. Although they belong to the same camp temporarily, they still have the idea of competing with each other. Both sides want to know who is strong and who is weak in talent and ability. Zhuge Liang's resourcefulness, such as borrowing the arrow of a straw boat and the east wind, made Zhou Yu very scared and said the classic sentence: "How can Yu Sheng see the light?" In fact, Zhou Yu is jealous that Zhuge Liang's talent is above him.
The second reason is that everyone has his own master and has to guard against it. In the book, Zhou Yu found Zhuge Liang's outstanding talent and was very jealous. Besides, they have different ideas. Zhou Yu holds the theory that the world is divided into two, while Zhuge Liang thinks that the world will be divided into three. So there must be a war between them. Moreover, the two sides serve different lords. Zhou Yu naturally cannot let Zhuge Liang, a menace, assist others and spoil his own good deeds. In addition, Zhou Yu in the book is narrow-minded and jealous of Zhuge Liang, which is why he has repeatedly embarrassed Zhuge Liang.
In Romance of the Three Kingdoms, Zhou Yu was proud of her spring breeze before meeting Zhuge Liang, and her love career was fruitful. However, because Zhuge Liang's ability was too strong, Zhou Yu's jealousy was aroused, and he was finally angry alive, which was really regrettable.