Claiming the USSR and Nazi Germany were allied is not only Nazi propaganda (aka ‘double genocide’ theory), but also holocaust denial. And, you know, a basic denial of reality.
It should be noted that Poland invaded the Soviet Union during the Russian Civil War and opportunistically killed tens of thousands of Jews. The Soviet Union, by the accounts of many Jewish and Slavic survivors of the holocaust, saved hundreds of thousands of lives and won the war by not only signing that NAP, but also making sure that the Nazis were not occupying vast swathes of territory in western Belarus and Ukraine that had tons of vulnerable groups in them. The price for being an antisemite was death in the Soviet Union.
I say this as someone whose family house was annexed by the Nazis, and our relatives house was torched and their kids were stolen away to the Rhineland, which we only learned of recently through genetic testing. We just assumed they all died.
Poland went to war with basically all their neighbors at this point and were largely supplied by Germany. There are anxieties about this history to this day in Western Ukraine, Belarus, Slovakia, and Czechia, because the Poles massacred a lot of people. Its one thing to want independence, its another to massacre innocent civilians for fun.
It wasn’t ‘appeasement’, it was active collusion.
The Soviet Union had just got out of a Civil War and had almost no industry. They had roughly 10 years to build an industrial base capable of defeating what essentially amounted to all of mainland Europe. They were a feudal society before WW2 and were starting from scratch. And they won, so clearly what they did, communism, worked.