Why did feudal fragmentation begin?

Feudal fragmentation is an integral stage in the process of state formation. Almost all countries have gone through a fragmentation phase. For example, in Russia, political fragmentation began due to the fact that external aggression ceased to exist. The Russian principalities realized that there was no need for them to pay any more tribute in order to remain safe. Therefore, they isolated themselves and began to develop the internal structure. In many territories, economically and militarily strong centers have emerged, independent of each other.