Why did kievan russia gradually decline and final collapse in the 1200's

Kievan Russia's decline was marked by the emergence of powerful autonomous principalities and warfare among their princes. Kiev Rus became an increasingly complex state containing numerous principalities that engaged in political and economic competition; dynastic and ecclesiastic bonds provided cohesion among them.

During the eleventh and twelve century princely administration gradual replaced tribal allegiance and authority. Each prince maintain and commanded his own military force. As the dynasty grew larger its system of succession required revision. Controversy arose over the standards of eligibility and the lands subject to succession.

The changing political structure contributed to repeated dynastic conflicts over succession to the Kevian throne. Some princes became ineligible for the succession to Kiev and concentrated on developing their autonomous realms. Kiev was sacked two more times in 1203 and 1235. The conflict revealed the divergence between the southern and western principalities, which were deeply entangled in the conflicts over Kiev, and those of the north east, which were indifferent to them.

Kiev lost its central role, and Kievan Russia was disintegrating and left without effective defenses by the time of the Mongolian invasion of 1237.    

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.