In Russia, most people put some part of the blame on the WWI winning coalition for humiliating Germany too much and then failing to keep its power in check, leading to a large, angry Germany in 1939.
The lands the USSR has occupied in 1939 are mostly Russian Empire lands, so USSR never really agreed to part with those. Neither was Germany committed to parting with its German Empire lands. You may argue they have both "signed something", right.
If you praise Germany for changing its strategy after 1945 to avert future wars, at the same time you should blame the US world order for failing to part with strategy which got them WWII after WWI, when dealing with post-Soviet Russia.
As they should have noticed by that moment, you do not get into stable, reciprocital relationship with someone you've either raped into signing a piece of paper or got them to sign for a $2.99 can of food or starve. I believe Soviet troops in 1945 Berlin did not have such expectations, but to my surprise, US and its thralls still do.
However, I'm also no big fun of the state of Ukraine, but I'm quite fond of Crimea. Many Ukrainian cities as well, but Crimea in particular.
So, as Lenin has said, "one can't live in a society and be free of that society".