Feudalism is the prevailing social framework in medieval Europe, in which the honorability held grounds from the Crown in return for military administration, and vassals were thusly inhabitants of the nobles, while the workers were obliged to live on their ruler's property and give him reverence, work, and an offer of the deliver, notionally in return for military insurance.
The correct answer is: because he can react to emergencies more quickly than Congress.
The president can appropriate government money in times of a disaster, to react to emergencies quicker than the Congress.
This situation only happens in times of emergency, in which the President is allowed to override the Congress and deliver executive orders without the Congress permission.
These emergencies are declared when: there is an armed conflict, a natural disaster, civil unrest, etc.