First of all, we should look for problems from Mohist thought itself. Everyone has heard of the idiom "sticking to the rules". At first, it was used to describe Mohist guarding the city, but later it gradually derived the meaning of sticking to the old law. The semantic change of this idiom is also a true reflection of the development of Mohist thought. Since Mozi, the founder of Mohism, founded Mohism, there has been no great innovation in Mohism. All are the same as Mozi's. In the process of rapid development of this era, backwardness is inevitable. Different from other schools of thought, Taoism has Zhuangzi after Laozi, Confucianism has Mencius after Confucius, and there are many talented legalists: Guan Zhong, Shang Yang, Wuqi, Han Fei, Li Si and so on. It is difficult for Mohist school to inherit and develop his theory after Mozi. We can't talk about those who can move on. Mohism is so powerful, but the younger generation only knows how to chew on the old capital.
And Mohism represents the interests of the middle and lower classes. This fundamentally determines that Mohist thought is difficult to be recognized by the rulers, let alone reused. After Confucianism was favored by the rulers, Mohism, which stood on the opposite side of Confucianism, was hit and rejected more. As the saying goes, "goodness is like water", legalists, Confucianists and other rulers will naturally follow suit. As for Mohism, my grandmother didn't love my uncle, so she was naturally abandoned and despised by my shoes. Incense is not passed down, and Mohism is difficult to continue. Moreover, Mohism, which represents the interests of the middle and lower classes, has a market only in the era of decentralization struggle. When the society moves towards a unified culture, Mohism will no longer be useful.
What's more, Mohism itself has committed crimes and can't live. It turns out that Mohism should be able to occupy a certain position by virtue of Mozi's powerful and overbearing guarding city. But after Mozi's death, the bad descendants of Mohism are still divided. There are three types of ink in Li Xiang, Dan Ling and Xiangfu. Although they have made little academic achievements, it is difficult for them to form a joint force and board the elegant hall. It is not surprising that the divided Mohist school has become a minority and a separation of powers. Of course, the decline of Mohist thought must also have the role of external forces. The rulers only attach importance to Mohist guarding the city, and regard other Mohist thoughts as "ingenious techniques" and discard them. Although some people regard the Mohist guild as an armed organization of Mohism, it is actually more similar to today's political parties. Unfortunately, the rulers can't see this. What feudal rulers can't tolerate most is that party organizations such as "party struggle" broke away from the normal social ruling order at that time, and were naturally regarded as a thorn in the flesh, and then quickly. Qin Shihuang's "burning books to bury Confucianism" and Hanwu's "abolishing a hundred schools of thought and respecting Confucianism" completely swept Mohist thought into the old pile of history. Mohism has also been completely squeezed out of the main channel of China culture.