Why there were no new nomads in the desert after the fall of the Mongols

Let me start by asking you to think about it, where did the nomads that ruled the Mongolian steppe before the Mongols go?

What about the Huns, the Turks, the Xianbei and so on, they have all disappeared into history.

I think so.

Every nomadic people who ruled the Mongolian steppe before the Mongols, they were eventually assimilated by the Han. Meanwhile other peoples who were relatively backward in the Mongolian steppe filled the void and ruled the Mongolian steppe. In the end, this ethnic group assimilated again, and another ethnic group filled the gap.

And the Mongols were not fully assimilated by the Han in the end. So there was no room for the rise of other nomadic peoples.