Why did Thomas Mann leave Germany after Adolf Hitler became chancellor in 1933?

When Adolf Hitler became chancellor in early 1933, Thomas Mann and his wife were on holiday in Switzerland. They were warned by their children in Munich not to return to Germany, as Mann had been a vocal critic of the National Socialists and their "inhuman fanaticism."1

Mann had long used his literary and cultural essays to defend humaneness, tolerance, and reason against political extremism. In 1930, he delivered a courageous address in Berlin, "An Appeal to Reason," in which he advocated for a common front between the cultured bourgeoisie and the Socialist working class to oppose the Nazis. Because of his steadfast opposition to Nazi policy, he became a target of the regime, eventually leading to the revocation of his German citizenship in 1936 and the withdrawal of an honorary doctorate from the University of Bonn. Choosing to remain in exile, Mann lived in Switzerland and later the United States, ultimately refusing to return to Germany to live even after the war.1