The idea that prejudice has a root cause in a series of personal events in an individual's life is false; whatever personal events may have shaped Hitler, anti-semitism in German and Austrian culture at the time was pervasive and helped shape the man and his narrative of racial prejudice. I'd like to point to our FAQ on the subject, especially u/commiespaceinvader and u/kieslowskifan's answers. I would only like to add that Hitler's book Mein Kampf, while it portrays a kind of fall into antisemitism, should not be taken at face value. Hitler wrote the book as propaganda, to perpetuate a world view he had already committed himself to.