Star Wars isn't taking from the Nazis when it comes to the Empire so much as it's borrowing from the visual imagery of German filmmaker Leni Riefenstahl. The Empire itself borrows the visual language of dictatorships throughout the 20th century as well as the Roman Empire.
If you read a more modern accounting of WW2, Nazi Germany wasn't the military powerhouse Hollywood portrays it as. Not to downplay the genocide and the other atrocities but Hitler failed forward quite a bit and Europe, post WW1, wasn't in much shape to oppose him. Also, Nazism was an ideology and the Galactic Empire and the First Order don't have an ideology, other than "control everything" and "wear black."
Edited by Concise Locket