What are the causes of feudal fragmentation?

The reasons for the feudal fragmentation of Kievan Rus: the development of cities as separate centers of craft and trade, subsistence farming occupies a leading position, the path “from the Varangians to the Greeks” has lost its significant position, the prince of Kiev gave the vassals the right to court, collect taxes, land becomes the main value, great growth productive forces, strengthening the authority of local princes, weakening the country’s defenses, increasing the pressure of the steppe nomads, Ancient Russia lost its role as an intermediary in trade relations between Western European and Eastern countries.