As Hitler was able to bring the populace more to his side and increase the manpower input to the SS or schutzstaffel it allowed for mass genocide. Also as the war carried on and the Germans began to lose the war resentment broke out even worst. Also the events leading up to cause genocide was the invasion of Poland and Russia since they both held the largest populations of Jews in Europe at the time and it was able to be done out side of Germany and secretive allowing for harsher treatment and events such as krystalnacht and the creation of ghettos