He moved to Germany just before WWI. I think he was eligible to stand in their Parliament as a WWI veteran (but I could be wrong). Most countries require citizenship to stand for their Parliament. I think he had German citizenship.
Hitler hated the Viennese culture for rejecting him, and Vienna was a thriving hub of Jewish art and intelligentsia. So the “Hitler failed art school and that caused WWII” has some truth, but it simplifies it too much.
Hitler was deadly afraid that he was part Jewish on the Polzl side (I think a great grandmother).
His story is quite instructive. He hated everything that he most feared in himself, and set out to destroy it. When he failed to destroy the things that represented his demons (his “Jewish side” in the final solution, Slavic and Russian communists who were in his neighbourhood in 1944 he then destroyed those things in himself and could only do so by killing himself. The Americans and British had early forensic psychiatrists studying him. They predicted that if he failed, Hitler would destroy his country and kill himself.
I have a book called “Hitler’s psychopathology”. It focuses on these aspects. I’ll take a pic and meme it when I find it. There are also artworks and books from Holocaust survivors. Primo Levi, Victor Frankl and many others were published. It’s not just The Diary of Ann Frank.