Don´t want to flood the forum.
In german historiography it is an agreed fact, that the Weimar Republic had three reasons why it ended in a dictatorship:
1. The Constitution was remarkably free and open, but had no safeguards against any who simply worked against it.
2. Some Institutions had "unhealthy" powers, i.e. the President. He had the right to rule under Art. 48 by "Notverordnung". These were presidential orders which overuled in cases of emergency everything. The emergency was declared by the president. Also he had the right to dissolve the parliament. Which was done often-
3. Nazis and Communists alike were able to openly work against the Republic. They wanted either the dictatorship or Communism.
Childish? Look it up, there is a picture of that 9-11 Inside job guy next to it.