For most of my life, I believed that British resistance, D-Day, and the Western front were the primary reasons for German defeat. That's certainly how it appeared to a lay person. It was only recently that I realised the vital role the Eastern front played in Nazi defeat.
https://en.m.wikipedia.org/wiki/German_casualties_in_World_W...
The Nazis lost over two million soldiers in the Eastern front, whereas all the other fronts combined produced a loss of ~800k soldiers. The turning point of the war came in Stalingrad, an entire year before D-Day even started.
The Soviet Union has been a brutal regime and I'm glad they lost the cold war. But the Russian people deserve more credit than they are being given for turning back the Nazi tide.