How did racism and intolerance contribute to World War 2?

Answer 1

because Hitler hated Jewish people and wanted to get rid of them and 'clean' the world of 'bad people'.

Addendum:More accurately, Hitler used the differences of several ethnic groups to focus the attention of the German people away from the totalitarian policies of the Nazi party, and to give the country a "common enemy" against whom they could struggle to attain the goals of the Nazis.