The Mongols experience a relatively rapid decline…
1396 CE to 1539 CE
The Mongols experience a relatively rapid decline as an influential power.
One important factor is their failure to acculturate their subjects to Mongol social traditions.
Another is the fundamental contradiction of a feudal, essentially nomadic, society's attempting to perpetuate a stable, centrally administered empire.
The sheer size of the empire is reason enough for the Mongol collapse.
It is too large for one person to administer, as Genghis had realized, yet adequate coordination is impossible among the ruling elements after the split into khanates.
Possibly the most important single reason is the disproportionately small number of Mongol conquerors compared with the masses of subject peoples.