Lakowski,
I'm sure western powers and Hitler had something to do with russians winning
Hitler was probably most notably reason.
Stalingrad is probably most famous mistake that Hitler knewingly did in the war.
Then there is a serie of other weird commands from Hitler in 1941-42, where he passed his adjutants and commanders opinion.
Jasonc,
I wouldn't think that 76mm HE would be fine against 50-60mm armour