48 year old German here. My grandparents were born in the 1920s.
Here's what they told me about Hitler's regime.
In the 1920s, life in Germany was pleasant, so the Nazis didn't get all the support they needed because their fearmongering didn't work very well.
Then, the Black Friday crisis hit Germany hard. Harder than any other European nation. Huge unemployment, a lot of discontent and desperate people. The Nazis used that to their full advantage - many people fell for them, but still not the majority of Germans.
So my grandparents still didn't take them that seriously. Even those Germans who knew what the Nazis had planned couldn't believe they would really do it. Try imagining living in 1932. If someone told you about WWII and 6 million dead in concentration camps, would you really have been able to take that seriously?
Then, suddenly, Hitler came to power. Still, not the majority of people supported him - but it took mere weeks to take away all their civic rights, their right to protest, their right not to be detained without due process, their right not to be surveilled, their right to live in a home the police can't raid without reason. It all happened too quickly.
So they all became afraid - VERY afraid. And too many of them minded their own business, after all, if they were law abiding citizens, what did they have to fear, they thought.
The famous quote by Martin Niemöller illustrates it:
First they came for the Communists
And I did not speak out
Because I was not a Communist
Then they came for the Socialists
And I did not speak out
Because I was not a Socialist
Then they came for the trade unionists
And I did not speak out
Because I was not a trade unionist
Then they came for the Jews
And I did not speak out
Because I was not a Jew
Then they came for me
And there was no one left
To speak out for me
The bottom line is this - at no time during the entire Nazi regime were there enough people in Germany who could and would put up the resistance necessary to stop the Nazis. But there were always lots of people opposed to them, but intimidated into being silent.