Deleted member 1487
That is certainly what Hitler thought in 1941 and it didn't quite play out that way. I mean the reason it fell apart was the famines, defeats, and general undermining of the legitimacy of Stalin's rule, which was pretty much the formula of the fall of the Czar and the Habsburgs. That and the Germans really working on the ethnic separatism (eventually) of the Ukranians, who had the ability to build up their core of training manpower during the war and inherited so much German equipment at the end while the Soviets themselves were too weak and unstable to crack down on them effectively. When Stalin then went to purge Zhukov and the army fought back that was the end of the Soviet regime and the start of their warlord period. I know a lot of people think the collapse of Communism was inevitable due to the inherent contradictions of the system of the nature of the Soviet regime, but its pretty clear that the Nazi invasion and resulting problems ripped out the seems on all the sutures that they had used to stitch together their Red Empire. Good for the world, bad for Hitler that his prediction about the fall of the Soviets took longer than was needed to beat the Nazis. The post-Soviet communist intellectuals so have some points about the regime being an improvement over the Czarist state even with all the failings of the Soviets right up to the invasion, but then the war pretty much dashed it apart. Who knows what it would have turned into without the war or had the Japanese not invaded the east and allowed for US supplies to come in via Siberia.The wheels would've come off after Stalin's death - it was pretty much Stalin The Country when Barbarossa happened - but that's still a few more years of grace. God knows what that would've meant for post-war Europe. At the very least, all the intellectuals in post-war Paris wouldn't be touting how great Stalin's USSR was when they could actually see the fucking place.
Now to the OP, where did the Japanese get their OTL oil for the war? IIRC they had 2-3 years stockpiled and managed to stretch that out by severe rationing during the war; perhaps if they went south and caught everyone with their pants down in 1941 they could have taken the DEI and gotten all the oil they needed, plus all the minerals and destroyed the US defenses in the area, rather than the US building up first and catching the Japanese relatively unprepared and then having the DEI themselves to supply oil. Maybe then the US wouldn't have had to invade the Home Isles of the Japanese and then mainland Asia to wrap up the IJA on the continent in those murderous campaigns before even getting a foothold in Europe. If the Japanese stretched themselves out instead over the Pacific and Southeast and South Asia they could have been defeated guarding a wide perimeter and then by the time the US A-bombs were ready they'd have had them to use against Japan rather than Germany.
As it stood IOTL even with a Germany first program the war against Japan really got moving first to try and open up the Siberian ports to supply the Soviets so they wouldn't fall to the Nazis. That meant Operation Downfall because the US started so far forward when they got involved, which meant huge US losses pretty early into the conflict in the East, before they really got stuck in in Europe. So maybe if the Japanese attacked south they would have lasted longer and made it easier for the US to move against Europe first and been able to use less resources to fight through the island perimeter that Japanese would have erected, rather than having to go for the jugular against Japan in 1943 because they were pretty much already on their doorstep. That was a bloodbath pretty early on in the war that soured the US public and may have been the factor that made the 1944 election so close.
There are all sorts of huge butterflies really if the Japanese go south rather than north.