The Zhou and the Mandate of Heaven
When the Zhou overthrew the Shang, they faced an awkward question: if the Shang kings ruled by descent from the gods, what right did rebels have to replace them? Their answer was the Mandate of Heaven — heaven grants the right to rule to whoever governs justly, and withdraws it from whoever does not. Floods, famine, and defeat became evidence of a mandate lost. It was a theory of legitimacy that justified their own coup, and it outlived them by three thousand years: every Chinese dynasty afterward claimed it, and every rebel used it.
The story that justifies an order (divine right, mandate, ideology) loses credibility; the order it propped up follows.