Why didn't grumbling lead to open opposition?

The question could also be "Why didn't another party take over?".
There was great fear of the SS they could destroy peoples lives so they were afraid to speak out.
Censorship - people didn't know exactly what the Nazis were doing and what their plans were. Extreme policies kept a secret.
Opposition was divided - They didn't trust each other to group against the Nazis - they were disorganised.
Votes - people had voted Hitler in so they could only expect him to do what he wanted.
Unpopular policies - policies that people did complain about were dropped.
In general people were pleased with the Nazis.