Adolf Hitler wasn't born in Germany. He was born in Austria to Austrian parents.
He only became a German citizen in 1932, less than a year before he came to power in Germany.
Did the Germans never question Hitler's Austrian origin? Why did the Germans allow an Austrian to rule them?
I'm sure many people think that Hitler was German because he led Germany and spoke German, but he was actually an Austrian.
I found answers about Hitler's immigration status by /u/kieslowskifan and /u/Georgy_K_Zhukov for a similar question from earlier in the month.
Others may have more answers.