Zhou rulers claimed that they had won the Mandate of Heaven because they
were believed to have the divine approval to rule. They believed that their reign was justified and legitimate because they had the favor and support of the gods. This idea of the Mandate of Heaven, which was deeply rooted in Confucianism, provided the ruler with both a moral and political basis for their power.
According to this belief, rulers were expected to act with virtue and benevolence, serving as a role model for their subjects. If a ruler failed to uphold these ideals and became tyrannical or oppressive, it was believed that they would lose the Mandate of Heaven.
This concept also provided a way for rival rulers to justify their efforts to overthrow a dynasty. If a ruler was seen as no longer having the Mandate of Heaven due to their misrule, another ruler could step in and claim the divine approval to rule.
Overall, the claim to the Mandate of Heaven was used by Zhou rulers as a way to maintain their hold on political power and to validate their right to rule over the people of China. It provided a moral and spiritual dimension to their authority, making them more than just political leaders.