Because of the emperor's suspicion. In ancient times, most emperors were very suspicious. They are afraid that their throne will be taken away by others, so they are very cautious about their heroes. Just in case, some people even killed their former heroes. They feel that only in this way can they keep their throne.

For example, Zhu Yuanzhang, who was also an emperor, killed many famous men in order to keep the throne. Zhu Yuanzhang changed from a commoner to an emperor. He felt that his throne was even harder to come by, and he should cherish his hard-won throne. First, he killed all the heroes who made great contributions to himself. He felt that only in this way could he keep his throne. Later, his doubts became more and more serious. As long as a minister says something bad, he feels that this minister has the heart of rebellion. He will kill the minister just in case. At that time, he also forced a general who was very useful to him to death. Because he was afraid that the general would rebel in the future, he felt that he would rather kill by mistake.

There are many emperors who are very suspicious. When they became emperors, they felt that the throne was in their own hands and could not be taken away by others, so they would kill some ministers who threatened them. In this way, they can prevent their throne from being taken away by those ministers. When these emperors went to kill those ministers, they never considered how much contribution these ministers had made to them before. They only feel that these ministers have contributed to them before, but they may become their biggest threat later.

Therefore, many loyal ministers in history have a bad end. They were loyal to the emperor all their lives, but they were usually executed by the emperor.