For much of the populace, sentiment only began to shift when life got harder for them personally. For some, that was when their children were killed in the war, for others it was when food shortages started to hurt, and still others would fully support the reich until it inevitably turned against them. Most personal impact that people felt was brushed off as "patriotic sacrifice" for the greater good. It was a bunch of small things that just piled up over time. Different people had different breaking points. But some people went through the whole war remaining fully supportive of the government.

You have to remember that propaganda was also much more effective then, when the government could fully control all media. Many Nazi supporters at the time had no idea what Hitler was really like or what was going on at concentration camps. The guards for those camps and other SS soldiers were chosen because they met certain loyalty criteria and would not go against orders. But everyone else was either oblivious to the cruelty, fearful of what would happen to their families if they went against the government, or just blissfully unaware and brainwashed by propaganda.

With the Internet today, it should be harder for people to fall for propaganda. The Internet really changes things now. You can see the disinformation influence everywhere but it's much harder to silence all the dissenters now. There will always be people who refuse to seek answers or listen to opposing viewpoints and there's not much to be done about that except teach open mindedness to children when they're young. It's why the fascists try to hard to simultaneously control and hamstring the education system. Unfortunately, they've been at it so long that there's now a large portion of the population that grew up with poor education and are now easily influenced by the media sources that the fascists control. The propaganda today must focus more on convincing people that there is an existential threat in the form of a group, person, or ideology that only they can stop. They just need to convince enough people that doing evil things for "good" reasons is justified. They're beginning to reach critical mass of supporters to where they can brazenly try to seize control of the government now, laws be damned. You see them pushing on those legal boundaries much more frequently these days. If they succeed, things will get worse for everyone (including their supporters) when they decide to fully drop their facades and begin doing evil things without any justification besides "because I felt like it". Leopards will always eat faces, but for some reason people never learn that lesson.