Getting the Soviets able to invade Germany early, and succeed, requires a PoD far enough back (it takes serious time and money to modernize an army) that the butterflies might just take out the Nazis - if the Soviets are ramping up their military in the early 30s, then even the mainstream political groups in Germany are going to see them as a threat. Hitler came to power in January 1933, and the Soviets would have been rebuilding by then.
His brand of crazy loses a lot of value when there is a real, tangible threat right on the border. You might even see France backing down and allowing Germany to re-arm just to deal with the threat (because Lord knows the French don't want to have to fight the Soviets!)