Among other factors mentioned in his book A HISTORY OF RUSSIA, Nicholas Riasanovsky notes that Soviet historians blamed feudalism as a major factor for the fall of Kievan Rus. Were they being defensive given that feudalism was considered one of the 'ills of capitalist society'. Or was it the choice of the Grand Prince to subdivide the Kievan state into different kingdoms ruled by his sons instead of applying primogeniture. (You see, some historians have convoluted history).