No. Soviets won the war because the Nazi's attacked them, there would not be the level of motivation among the troops for an offensive. Being invaded by an enemy that wants to murder you unconditionally is the most blank check one can receive from your citizens. The Soviets had more or less(save Finland) reached the pinnacle of what a Russia based empire could achieve territoriality on it's western border. Remember in the Cold War, what did the Soviet's directly take besides Prussia which is a Cato the Elder kind of thing? What were the Soviets supposed too, Russians fought Germans in WWI because the Germans were allies with countries that had things Russia wanted(including the Tsar's self respect). That's why Stalin took the no aggression pact with the guy who wrote a book about murdering all the people in his country, Soviets got considerably more land from that deal for considerably less effort than the Germans did and it doubled as insurance if Hitler would do what he ended up doing. That buffer zone took the brunt of Barabarossa and likely changed the outcome. Stalin wasn't stupid for taking that alliance he was stupid for not believing Hitler would attack and relying on Hitler acting like a homicidal lunatic to save him.
Your last question is an internal contradiction I hear often. WWII in Europe was all but over in 1941 without Hitler attacking the USSR. So yes all he had to do was nothing and he won WWII, in 1940 the war was covered as basically the Germans winning, the end, Hitler chose to flip that book to a new page. But invading the USSR wasn't a means to an end, it's the end itself. You can't negotiate with people about their end goals so of course he was going to attack the USSR. So it's hard to call it a mistake, we just think his end goal was stupid but that was his end goal and while there's things he could have done different to change the outcome the biggest thing he could have done was to not be him and not have his homicidal goals in the first place. A generic Fascist, socialist, conservative, liberal doesn't matter, if they hadn't tried massacring the USSR's population they win. Russia buckled under far less mortal stress in 1917 because it was an ordinary war and the political consequences of losing mostly were better for the average person than fighting on. If the alternative to victory is death and you've got three times as many bodies as the person trying to kill you, you got a good chance.
