weimar republic was largly due to the great depression and the treaty of versillies that acted as tools of propaganda for the Nais in order to gain support, those were the big ones, other include communist threat, removal of communist threat, Hitlers trial after the putsch, Im sure there are more, but its been 3yrs, so I'll edit if I can think of more
Alot more to it than that, but in a nut shell thats it. Never studied the German empire though...