Feudalism was a decentralized organization that arose when central authority did not perform its functions and when it could not prevent the rise of local powers. Rome crumbled.
With the decline of Rome, the loss of her institutions of control failed also. Land became the engine of the age and the human vassal was the tool that maintained it.
The advantages and disadvantages of feudalism can only be explored by recognizing the different viewpoints of those involved. The greatest strength was in protection. The landholding class of nobles offered protection to those that served them.
Within this institution of aristocracy, social stratification adapted to a moneyless economy. Civil and military power at the local level created semi-independent local governments that defended against bandit and brigands. This eventually evolved into highly diverse forms of customs based on servitude and heredity. The wealthy gained more land as those seeking protection established relationships with them by giving their oaths of life. Land was equal to power and a noble was equal to safety.
The land would not be one.
The sweet taste of power is one that was not given up easily. Landowners (Nobles) developed military forces and their own sub-cultures within the boundaries of their lands. The nation displayed the same failures as the Greek world.
A broken land has a broken people. A broken government has a broken rule. This division caused the quick growth and decline of feudalism. This created the emphasis on contractual agreements and the deliverance on authority to an expanded group of individuals. The ruling of the land by one individual would be even more difficult now that others have tasted some of the same fruit.