What's the enemy between Hitler and the Jews? Why kill all the Jews?

This has always been an elusive mystery. After Hitler's mother got cancer, a local Jewish doctor (Eduard Bloch) gave her almost free care (at that time, Hitler's family could hardly afford medical expenses economically). After her death, Hitler, a teenager, stood beside her sister and declared in front of the old doctor, "I will never forget this kindness." Many years later, when he was still wandering in Vienna, he once sent some of his oil paintings to the doctor. When the Third Reich successfully annexed Austria, Hitler told the local Nazi official Dr. Bloch that he was a "noble Jew". Bloch even remembers that Hitler's motorcade stopped at his window when it passed his clinic, giving them some special circumstances, such as not needing to put yellow satellites on their clothes and gesturing to let the local police station release Dr. Bloch's daughter's fiance. Later, they also successfully fled Austria and immigrated to the United States.

In addition, the Iron Cross medal won by Hitler during World War I was also awarded by a Jewish officer (Hugo guttmann). After the Nazi government began its official anti-Semitic policy, guttmann did not lose his pension and rank like other Jewish German veterans.

Why did Hitler still have such a great anti-Semitic tendency after such contact with Jews, and even contributed to the almost unprecedented massacre in the history of Western Europe? It has always been a mystery whether he was hostile to Jews by the whole continental European society at that time, or whether he began to form a world outlook in his own mind on faith or race.