seems 20 times bigger than the gap between the top and bottom in Poland
Russia, since time immemorial, was a place of two separate countries. One for the "Muzhiki", or "average man", and one for the "Gospoda" (gentry).
The type of hatred and derision reserved for the "average man", was worse than the Southern plantation owners had for the Negr0es.
We literally kept our own kin in chains of slavery, until 1861. Not blacks from Africa, or Jews from Spain - but our own people.
Many Russian authors wrote about this disgusting aspect of national life, from Saltykov-Shedrin, to Tolstoy.
It's why the Bolsheviks could storm into power, and use past sins as a catch-all excuse for the horrors they unleashed in turn.
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As you probably know, Russia's literate classes for a long time didn't even speak Russian at home. Only French and English and German.
It's good, that Poland did not absorb at least this aspect of the Russian way of organizing society.