Hitler didn’t start with the camps. He started with banning books, cancelling the press, targeting immigrants, turning neighbors into enemies, defunding the arts… and a big promise to make Germany great again. Remember that.
Don’t kid yourself. During that era of Germany’s history, there was (just as there is now in America) a majority that were eager to embrace fascism and most of what it brought. This is always a result of extreme leftist policies. Extremism on both sides is our problem. We need to meet somewhere in the middle if we ever want to defeat extreme policies from either side. JMHO.