It is possible to identify various causes responsible for the downfall of Delhi Sultanate.
Firstly, the rule of the sultans of the Delhi was based on their military strength, and not on the willing support of the people.
Thus the foundation of the Sultanate rule was weak from the very beginning.
Secondly, the institution of slavery was another weakness from which the Delhi Sultanate suffered.
In course of time the slaves had become an important political force to reckon with.
Thirdly, the nobility that had been an important pillar of administration no longer could help the administration because of their inefficiency.
The inefficient nobility became a liability to the administration. Fourthly, external factors also contributed to the fall of the Delhi Sultanate.
After the invasion of Tamerlane (Timur) in 1398, the first battle of Panipat in 1526 finally sealed the fate of the Delhi Sultanate.