German "strategy" certainly helped.
Had they kept Hitler's egomaniacal lust to crush Stalingrad itself at bay and instead simply encircled Stalingrad to cut off its supplies and proceed to take the Caucasus oil fields instead, the whole war could have turned differently.
The German generals (and to a lesser extant Hitler) knew Russia could ramp up tank production fast and had way more soldiers then them if it turned into trench warfare or even total warfare level tank vs tank or aircraft vs aircraft fights. Largely because Germany already had to deal with the UK+America+Canada on the other front and we themselves limited in their own production ability vs the much larger Russia (regardless if the Russian industry was less advanced, it was still more advanced than the biased Germans expected the slavs to be).
The simple fact the Russian's had ANY tanks that they couldn't easily deal with, let alone not destroy at all with their own tanks, totally caught the Nazi generals off guard and slowed the whole invasion down.
The technological advantage that Russia had early on can not be downplayed. It was absolutely critical.