Mistrust of the Weimar government stemming from the Treaty, was based considerably on the "stab in the back" legend. In November 1918, Germany's armies were being routed in the West, the Bulgarians, Turks and Austro-Hungarians were suing for peace, thus exposing Germany's southern borders to potential allied attacks, the Blockade was starving the civilians out, and revolution had brought down the monarchy. Despite all of this, members of the Military and the Far Right primarily, created a myth that Germany had simply been stabbed in the back, variously by Jews, communists, socialists and weak-willed civilians. Because the German Army was victorious in the east, still in the field in the west, and no enemy occupied their territory, Germany had not been beaten.
So, when the Social Democrats were advised by their military advisors to sign an armistice and then accept a peace treaty, neither of which was terribly appealing to Germans, the Weimar government was seen as having sold out the German people, and the Military largely escaped any blame for having gotten Germany in this mess in the first place, and for advising the government to accept the armistice AND the peace treaty.
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