Russians... well, they simply hated Germans.
It is hard to explain to guy from US how does it feels like when your family if massacred by Germans, town or village burned to the grounds, people that you know treated like an animals.
You see, when those Russian soldiers pushed back Nazis, They found mass-graves filled with thens of thousands of their compatriots, they found gallons on town squares on whose Germans hung civilians 14-80 y/o.
Germans used to have in Russia and Serbia 100:1 ratio.
100 shot civilians for each killed German soldiers.
remember that those Russian soldiers liberated Treblinka and Auschwitz.
After all of that, they simply didn't gave a damn about Germans. All they wanted is revenge, and they considered that most holly thing to do.
“how does it feels like when your family if massacred by Germans,”
how does the amish in germany feel when the communists murdered half a million germans in 1921.
http://www.lib.ndsu.nodak.edu/grhc/order/general/sinner.html
the russians you like so much are the biggest murderers in the history of the world.
I can see your point of view. From a historical aspect, you would have have been better off to be invaded by the Mongols than by the Nazis. At least with the Mongols, you were sometimes given a chance to Give Tribute and avoid annihilation.