We actually saw it from the other point of view. Tons of cultures from China to the Americas and the Pacific have had vast empires that historians are just now realizing existed. The cultures followed the same path you see now, including deprecating themselves to help the lesser cultures rise up. When the cultures begin to equalize the choice then comes to stop the deprecation or continue. It is also up to the new culture to believe they are dominating by their greatness or recognize what actually happened. Right now we are choosing to let the other cultures win.