If you mean Nazi Germany then your example is indeed quite interesting. Hitler did not come to power through mass consensus, or really any consensus. He came to power through political maneuvering. The Nazi's largest victory in anything like an open election was in mid 1932 [1] where they gained 37% of the vote. Failing to form a government, a new election was called in late 1932 [2] where the Nazis were down to 33% support.

In spite of the lack of support, Hitler gained the chancellorship through a series of fortunate (for him) events and backroom dealings. His supporters then escalated things they had already been doing which included disrupting meetings of opposition, preventing their speakers from speaking, engage in often violent conflict with supporters of other groups, and so on. This culminated then with the formal banning of speech that spoke negatively of their politics. The net effect of this was that in 1933 [3] the Nazis managed to get 44% of the vote.

After that, the ban on free speech and politics was escalated with him ultimately banning all political parties except the Nazi party. Had Germany had strong and real protections of free speech, it's very likely that the Nazis would never have been able to come to power. And they certainly would not have been able to hold onto it. And this is a recurring theme in nations that end up going down the path tyranny and oppression. The first thing to go is free speech, often started on the ground level by political supporters who work to stop people they disagree with from being able to speak.

It's easy to condemn things in hindsight and claim people should have seen what was coming. But that's disingenuous. People generally want to do the right thing, though we all disagree on what right is. Germany and the German people were struggling and felt they were being exploited by capitalism and certain unfairly privileged groups within society. Hitler used this to gain a minority support of people by with rousing talks against capitalism and against the privileged few. Few were thinking about the implications of such rhetoric -- the dangers of when groups become mobs.

[1] - https://en.wikipedia.org/wiki/German_federal_election,_July_...

[2] - https://en.wikipedia.org/wiki/German_federal_election,_Novem...

[3] - https://en.wikipedia.org/wiki/German_federal_election,_March...