Sadly, most people just didn't care, didn't know or simply created a new narrative in their minds.

i've seen it happen to Russians now, people who were pretty normal, just refuse to believe their government could be doing something wrong and that they (Russia) is 'defending themselves'

mental gymnastics 101

in fact, in Hitlers speech when declaring war, it sounds like Putin, 'the European powers are making me do it, we must protect the German speakers in the Sudetenland etc