Many families have gradually declined for such reasons, and this is not something that has happened just once or twice or even at frequent intervals. The Primordial World has a history of over a thousand years, though under the premise of having rulers, there have only been eight hundred years. In these eight hundred years, the entire world was governed by different rulers. The reason for constant changes is that the progeny of these rulers lacked the true ability to govern the entire world.
For a long time, many rulers pondered over this question: how to ensure that the dynasty they created would not fall under the control of others. While this is evidently a difficult problem to solve, if one wishes to keep ruling their world continuously, then the inevitable conclusion is that this problem must be addressed.