That was OK. Happened in 1932-1933, and it was not a landslide victory, with only 33-44% of votes. The Holocaust and WW2 were not OK, but they happened in 1941-1945 and 1939-1945 respectively, long after the democratic institutions in Germany were dismantled in 1933-34.
> I'd argue that democracy can only work if there are mechanisms to protect the minorities from the majority.
Not sure I follow. Do you think Mark Zuckerberg, Larry Page, Jack Dorsey and other shareholders of FB/Alphabet/Twitter are a minority who need protection from being oppressed?