Saints are fickle and take the people as their heart. What do you mean?

Laozi said that "saints are fickle and take people's hearts as their heart", which is not only Mao Zedong's "serving the people wholeheartedly", but also his own heart, which is selfish in common parlance. For example, I said this to convince the king. In the eyes of kings, only saints can be admired. The code of conduct of saints can be used as a model for kings, thus gaining the support of the people. Secondly, I think this sentence means to respect Wang Weimin's ideas and care about people's sufferings. The philosophy contained in it should imply that man is water, not soil, and can carry a boat or overturn it.