Hitler attacked Russians after his recon and secret services confirmed that they are building a massive military force on their western border and it's only a matter of time before they launch a full scale invasion with the idea of taking the entire Europe in one massive campaign. Hitler decided to go with an immediate preemptive strike as this was the only hope of keeping them back. He tried to get Franco in Spain to join the Axis, but he chicken out and remained neutral. Having him watch Hitler's back would 100% help in crushing Day-D invasion. Japs were supposed to attack Russia from the back and they agreed to this plan. Not only did they not do it in the end, but they allowed Americans to go through and enter Soviet Union from East and provide them with support, mainly resources and fuel which was critical. Even with all of these setbacks, Europeans were absolutely kicking Soviet's assess and what cost us the victory in the end was lack of resources, as fighting on multiple fronts got us to quickly run out of fuel and therefore the ability to supply the troops was finished. Still, the result was that there was no more chance of Soviets having the capacity to take the whole Europe, their master plan was fucked, and all jews could do now is go back into hiding and work from shadows as they have for the las 100 years, even if they won they have been heavily wounded. If he didn't pull this off, 1984 would be nothing compared to how things would be now.