....the Mongol invasions from the East. Kiev to the south was the centre of the Eastern Slavic culture at the time, but, being in the plains/steppes, it went down before the Golden Horde and was destroyed. The town (town, not city) of Moscow to the north was protected to some extent by dense forests, impenetrable to the Khan's cavalry. It became the preeminent focus of Slavic resistance.
In a nutshell.....Russia missed out on the Renaissance because it was under Mogol occupation. The Russians to this day refer to this as the 'Tartar Yoke'. Though their culture seemed to absorb some of the characteristics of the Horde. They say, "Scratch a Russian, and underneath you'll find a Tartar'.
This was one of the reasons for the Russians eventual advancement to Vladivostok. To advance up the invasion superhighway of the steppes, down which the Huns and Mongols, etc had driven westward into Europe, and dry up the invasive malignancy at its source.