Complex sentence: The military defeat in World War I and the economic problems thereafter asked for a scapegoat: the Jews (with a marginal percentage of 0,9% of the German population) and their relatively good economic position made them the ideal target.
Split into simpler sentences: The military defeat in World War I and the economic problems thereafter called for a scapegoat. The Jews with a marginal percentage of 0.9% of the German population and their relatively good economic position made them the ideal target.