Why is the 42-episode TV series The Big Sophora Tree banned?

It is said that it involves politically sensitive topics.

Plot summary: There has been a folk proverb since ancient times: "Ask me where my ancestors came from, there is a big locust tree in Hongdong, Shanxi." The Hongwu immigrants not only reasonably distributed the living space of the population, but also had cultural differences with the local indigenous people. After long-term integration and exchange in terms of psychology and customs, regional civilizations will inevitably take care of each other and cultivate new civilization seeds, which has played an important role in the great integration of the Chinese nation. It left a profound mark in the history of ancient Chinese immigration, laid the foundation for the Ming Empire to become the most powerful country in the world at that time, and contributed to the development of Chinese national culture.