When I was a kid and learned about the Holocaust I used to wonder the same thing. I don’t know.
When I was a kid I thought the WWII Germans were so cool because they had some awesome uniforms. My aunt set me straight about the Holocaust and to this day I abhor what Germany allowed Hitler to do and the many who went along with it or simply did nothing to stop it.
If we see evil happening it is our duty as a human being to try and stop it.