• The Cambridge History of Russia asserts that the arrival of the Khans put the authoritarian structure in place. Whereas previously, Russia/Kievan Rus had been ruled by a handful of bitter, petty Grand Princes, the arrival of the Mongols turned the whole power structure onto its head. The Principality of Vladimir-Suzdal was the first to submit voluntarily to the Khan, and as a result received special treatment for much of the Mongol period. Eventually the power base shifted from the provincial capital of Vladimir to Moscow, and the system of a singular autocrat had become the way of the land, at least in Muscovy, which would go on to absorb or inherit the rest of Rus.

• Poland wasn't particularly autocratic (and in fact was a remarkable liberal, if inefficient constitutional monarchy during much of the early modern period) until most of it was absorbed by Russia in 1795. It was then of course liberated after WWI, and then promptly made into a Soviet satellite in 1945.

• As far as the rest of Eastern Europe is concerned, the Balkans were divided between the Habsburg and Ottoman Empires for much of the Early Modern Period and kept relatively undeveloped. Most of these countries were gradually released throughout various wars through the 19th Century, with the rest (The Habsburg bits) in 1918. The image of this region being "totalitarian" and "oppressive" likely comes from when most of them (except Greece, which had its own problems under a military junta from 1967-1974) were turned into Soviet satellites like Poland. Yugoslavia was a notable exception, since, though he was a Communist, Tito was no friend of Stalin and actually a member of the non-aligned movement. Tito was, however, still a dictator, and debating his level of "oppression" is another issue entirely.

Edit: Removed an extra "throughout"