Edit: So I rambled a bit here, and didn't really mean, went a bit off the rails: To answer very quickly, from my studies it seems relatively obvious his ambitions would have inevitably gotten him into conflict with the Soviets, it's his timing in doing so that was both the thing that caught them off guard, and the thing that made them enter the war far earlier.

I'm afraid I have none of my old study / university stuff at hand so I really can't do much checking while im on my phone: But from memory, the Russians definitely didn't expect it, especially at that specific moment. There's stories of Stalin essentially going into seclusion for a few days / a week when he found out - the implication being it legitimately shocked him. There is some reasonable debate on that though, there's reasonable evidence to show that if nothing else in the days leading up to the invasion some members of the Soviets were aware of the chances of a German invasion. I think it's relatively self evident from the success of Barbarossa (Despite its inability to actually take Russia) in that if the Russian winter hadn't rolled in when it did, the Russians really didn't stand a chance.

Entirely talking from my own opinion here: The German war machine was nigh unstoppable if you remove the Russians on their eastern front, I can't remember exact statistics, but to give a bit of perspective, even when fighting various other campaigns: at no moment from operation Barbarossa to the end of the war was less than 70~% of the German force occupied fighting the Russians. The losses they experienced are truly, truly mind blowing to me. Someone can happily correct me on numbers here, but yeah.

It's the old saying, WW2 was fought on British Intelligence, American Steel and Russian Blood.