With the new parliamentary democracy came a new constitution which was introduced in June 1918 although some Germans felt that democracy had been pushed on to them. This allowed a president to be elected by the parliament. This posed problems though, the amount of votes received by a party in an election predicted the number of seats that they would be allocated in the parliament. Although this is a good idea in theory, it meant that many parties were formed as they all had a chance of winning seats and a majority party vote could not be achieved, at one time in Germany there were over 30 political parties elected into parliament. Some of the parties joined together to make coalition governments but as the parties had different aims making decisions was impossible.
The constitution also introduced Article 48 which allowed the president at the time to abandon democracy in an emergency.
This meant that the president could make decisions without the government, this meant that Germany was not really being run as a democracy under the Weimar Republic.
On the 28th June 1919 the Treaty of Versailles was signed. Lots of Germans including ex soldiers known as Freikorps were bitter about the terms in the treaty, they felt that they had been treated unfairly and that the terms were too harsh, especially the reparations that had to be paid. They had believed that they would have a lenient treaty.
As reparations were so high more money was printed to pay off debts and this caused inflation. When Germany fell behind with reparation payments to France, troops were sent into the Ruhr Valley to take industrial goods, as the Rhineland was a demilitarised zone, there were no German troops to defend it. Instead Germany used Passive Resistance, workers protested by striking. The German government supported the strikers by continuing to pay them a wage, more money was printed to do this and this caused Hyperinflation.
I think that the Treaty of Versailles was the most important reason why many Germans hated the Weimar Republic. Although many Germans did not like 1 and 2, I think that the Stab in the Back could have been forgiven and the new constitution would have finally been accepted. The Treaty was hated by the majority of the German population.