What are the advantages of ancient kings being passed on to the eldest son?

The eldest son inheritance system is determined by the patriarchal clan system and originated in the Western Zhou Dynasty. Because my son's biological mother is a queen or a palace, deliberate education and exercise have given her more opportunities than other brothers. In ancient times, succession to the throne was a struggle for power redistribution. Due to its orthodox relationship, Di Zi more or less eliminated some unstable factors (hostility between father and son, opposition between illegitimate children and consorts) and ensured the smooth handover of the throne. However, in ancient China, the right to inherit the eldest son was concentrated in the Western Zhou Dynasty and the early Spring and Autumn Period. Due to the collapse of rites and music in the Spring and Autumn Period and the Warring States Period, the patriarchal clan system was greatly challenged, and the eldest son had no obvious advantage in inheriting the throne. In ancient China, most emperors ascended the throne as illegitimate children.