Generally speaking, entrepreneurs are more powerful, and their civil servants and military commanders are more United and have a higher level. So at the beginning of a dynasty, politics was relatively clear and people's lives were relatively rich.
However, after several generations of monarchs, these monarchs have lived in a rich living environment since childhood, lacking understanding of the lives of people outside, and are willing to enjoy it. However, those in power have their own factions, vying for power and profits, marrying your preferences, and paying no attention to the lives of the bottom people. When the life of the people at the bottom is not guaranteed and their lives are in danger, they will naturally rise up against those in power.
For example, Chen Sheng and Guangwu Uprising in the Qin Dynasty, the Yellow Scarf Army at the end of the Han Dynasty, and the upper rulers enjoyed it, regardless of the lives of the people, and the people rose up, and smoke was everywhere at the end of Sui Dynasty. Isn't it also caused by Emperor Yang Di's heavy corvee, heavy taxes and belligerence that people's lives were not guaranteed?
Therefore, the division and integration in ancient history can be said to be inevitable, because the division and integration are due to the needs of the people and the needs of the people. When the ruler harms the broad masses of people, it will naturally lead to division. When people are eager for unity and harmony, they will naturally create heroes.