I know there are many reasons Nazi Germany lost the war, but i personally believe that if Nazi Germany did not invade Russia, breaking their treaty, Russia might have not had a stake in the war and wouldnt have pushed Nazi Germany all the way back to Berlin
The biggest flaw with this argument is the assumption that invading russia was an option.
One of the main reasons for starting World War two was to expand westwards towards the Urals to get "Lebensraum" for future german settlers.
I agree with the other comment, this topic comes up pretty often but the people neglect the fact that Barbarrosa was the point of WW2 in Europe and therefore hardly qualifies as "reason" for the loss since this would essentially mean "the reason for the loss was that they started the war in the first place".