I think that Hitler's desire to invade Russia stemmed largely from his desire to get at the large Jewish populations in order to kill them.
I’m not so sure. Certainly a driving force behind the invasion of Russia was to acquire that lebensraum which he outlined in Mein Kampf, but he also was convince (wrongly) that the fall of Russia would force Britain to sue for peace.
As far as killing the Jews, it seem that this was more a case of not having another means to get rid of them. Nazi policy had long been designed to drive the Jews away from German territory more than to exterminate them (though if they died in the process they didn’t care either). The plan to ship European Jews to Madagascar was a legitimate plan right into 1941. It just was never a practical plan. When the Nazis invaded Russia they knew they would be re-inheriting many Jews they had driven from Poland previously along with many new populations. I think it was decided at this point that since they can’t seem to be able to get rid of them, they were just going to have to kill them instead. This is why as of this point we still only have Einsatzgruppen committing mass killings in the east and don’t yet have mass gassing which is far more efficient. There are some gas vans in operation at this point but this still is not a very efficient method of mass killing. The process is still in development as it were. The beginning of next month there will finally be a mass gassing at Auschwitz and it wont even be Jews that are gassed. 600 Soviet P.O.W. will be the first mass gassing at the facility. Chelmo, the first purpose built extermination camp won’t open until December which is about the same time that the Wannsee Conference was originally scheduled to happen (establishing an official structure to the extermination project).
I think that if they initially wanted nothing else but the extermination of the Jews they would have never even entertained the many different schemes to eject them from Europe, and they would have committed more forces in North Africa so they could have driven into Palestine eliminating the Jews in their homeland. Also I think there would have been a better plan for extermination from the beginning of the invasion than what was in place.
You could be right but remember, to Hitler, as well as a large part of Fascism, the Jews and the Communists were considered basically the same entity for purposes of their philosophy.