Why did Kangxi Qianlong sweep Zhu Yuanzhang's grave?

The best way to realize that you are orthodox is to incense orthodoxy. The Qing government was a foreign regime, which was not recognized by the Central Plains people. There is a feeling similar to the present colony. Once this ethos pervades the whole country, Manchu rule will be threatened.

So in this case, the Qing government adopted two methods, one soft and the other hard. The hard part is the literary inquisition and braids. Through these two methods, the resistance of the Han people can be dispelled on the surface, and through long-term implementation, the Han people can be influenced subtly. The soft aspect is to show respect for China's traditional culture, such as making Han Chinese an official, offering incense to Confucius and giving titles to his descendants.

Moreover, considering the Han people's recognition of the Ming regime, they went to the Ming Tombs to offer sacrifices to heaven, saying that the Qing Dynasty won the world not because of how fast his knife was, but because the officials of the Ming Dynasty were really corrupt, and the Manchu people were totally doomed not to sit on the throne of the emperor.