The republic was seen as being closely associated with the Versailles Treaty and was thus unpopular from the outset.
Proportional representation led to a large number of small parties with little political clout. these hung on to the larger parties, who in turn relied upon these groups to stay in power. Little could be achieved in this political climate. progressive measures would be opposed by some within the coalition and would not see the light of day. It was this lack of strength and inability to unite that again led to the extremist movements of the right and left wing becoming more popular.
The president could, according to the constitution, rule by decree. This enabled Hitler, upon assuming the role, to legally take measures that ensured a rapid end to democracy within Germany.