Because after Zhuge Liang's death, Liu Chan abolished the prime minister system, so there was no prime minister from Zhuge Liang's death to the demise of Shu Han.

Since the establishment of Qin and Han Dynasties, the prime minister is the head of the three public offices, in charge of civil affairs, with too much power. Later generations continued to dilute the power of the prime minister. In the Eastern Han Dynasty, the official positions of Sangong were replaced by Stuart, Sikong, Sima and Prime Minister, and even their names were gone.

In Xian Di, Cao Cao took the emperor as a vassal for the convenience of being in charge of state affairs by himself. He restored the system in the early years of the Western Han Dynasty and became a prime minister himself. At the same time, he did not settle down, but seized military power and civil affairs.

When Liu Bei established Shu Han, he inherited the official system of Xian Di and took Zhuge Liang as the prime minister, because he nominally inherited the Han Dynasty usurped by Cao Pi. However, due to the excessive power of the Prime Minister, Liu Bei, as a lean man, never gave Zhuge Liang the power to open the government before his death, thus greatly limiting the authority of the post of Prime Minister.

When Liu Bei died, he had to entrust an orphan to Zhuge Liang, who opened a house to build a tooth and completely mastered the power of Shu Han. In fact, Liu Chan is overhead. Of course, Zhuge Liang's loyalty is beyond doubt, but Liu Chan is definitely not happy.

Therefore, after Zhuge's death, the prime minister system was abolished, and there was no prime minister in Shu until its demise.

After Zhuge Liang's death, Jiang Wan has been leading state affairs as the secretariat and secretary of Yizhou, but his power is far from Zhuge Liang's.

In addition, during the Qin and Han Dynasties, many scholars went out as generals and went in as ministers. They got on the horse to rule the army and got off the horse to rule the people. Like Jiang Wan, he later became a general. After his death, Fei Yi also recorded history and presided over state affairs as a general. So don't measure the situation from the perspective of the world. The distinction between the main army and the main people is not strict.

It was not until the death of Fei Yi that Jiang was promoted from General Wei to General Wei, but he always led the troops outside and never returned to Chengdu to preside over state affairs.