What historical circumstances led to the Feudalist Hierarchy in Europe.( Also Japan if u know the answer)

Fall of the Western Roman Empire.

Explanation:

After the fall of Western Roman Empire Germanic tribes settled and created many states on its soil. As it was hard to established certain political authority, rulers of these kingdoms introduced feudal system, that was based on loyalty. It was the dominant form throughout Middle Ages. In France for example lasted until the Revolution of 1789.

it is a because im a fod nigba