The decline of Constantinople – a main trading partner of Kievan Rus' – played a significant role in the decline of the Kievan Rus'. The trade route from the Varangians to the Greeks, along which the goods were moving from the Black Sea (mainly Byzantine) through eastern Europe to the Baltic, was a cornerstone of Kiev wealth and prosperity. Kiev was the main power and initiator in this relationship, once the Byzantine Empire fell into turmoil and the supplies became erratic, profits dried out, and Kiev lost its appeal.[citation needed]
Try to answer this question if possible (otherwise reply "unanswerable"): What was not a major cornerstone of Kiev wealth and prosperity?
unanswerable