Hitler believed that the Jewish people were responsible for events like losing the World War One and an economical crisis. Another reason could be Hitler's view that some races (the Aryan race) are more superior tank others inferior (the Jews.)
In order for Hitler to gain power, he needed a scapegoat. He blame the Semitic community (Jews) in order to relieve the German people of shame they felt due to the loss of WWI. He attempted to wipe out their population because they were inferior.
