The fundamental reason that great aristocratic clans could rule a region was that they were the local officials. As long as one is human, they cannot escape personal relationships. Additionally, during the Han Dynasty, the doctrines of filial piety and fraternal duty implicitly encouraged covering up for one's relatives. Therefore, it seemed only natural that serving as an official in one's hometown and seeking benefits for one's own family was both a natural inclination and an unspoken rule tacitly accepted by everyone.
As a result, local aristocratic families became increasingly entrenched, and their management of local affairs grew more and more effective. In times of peace, this could be described as a harmonious situation. However, if internal strife erupted, it would become extremely difficult to handle.