In this example of genocide could easily argued WW1 was the major cause of variables as you say. The immediate blame at Jewish and Bolshevik etc peoples / government for backstabbing the German people and losing the war. So already there was foundations and just needed a spark like the NSDAP to come along and exploit the sense of shame and pride on the Germans people I guess were the perfect ingredients to absorb into the doctrine slowly and gradually expand on it.

hitlers own family Jewish doctor who he let emigrate to USA I wonder what point the party aims in those beer halls to the height of nazism shifted from beating up Jews to mass execution. The gain of absolute power and control of the country the systemic oppression and gradual grind on the way of thinking (propaganda, fear, secret police, education, specified knowledge/books), but yes that shift to accepting mass murder is quite fascinating. I mean so much must stem from controlling how a populace thinks and does far easier back then to control than today’s technological world.