To be fair, they were one nation fighting everybody else on multiple fronts. I'm not hailing nazis.
Not about being Fair. If you don't want to have your buildings leveled, the cream of your youth killed, many of your women raped and possesions plundered, and your name ruined for a couple of generations, don't pick a fight with multiple powers, invade their lands, rape their women, plunder their riches, enslave their populace, etc. etc.
They had the advantage of surprise and good tactics (plus taking on only one opponent at a time) up until the end of '41. They were able to slog it out until the end of '42. But after that they lost about as fast as could be expected considering that no offensives ever covered more than 400-600km before needing a few months of reorganization and replenishment.