"Progressives should not make the same mistake that Ernst Thälmann made in 1932. The leader of the German Communist Party, Thälmann saw mainstream liberals as his enemies, and so the center and left never joined forces against the Nazis. Thälmann famously said that ‘some Nazi trees must not be allowed to overshadow a forest’ of social democrats, whom he sneeringly called ‘social fascists.’
After Adolf Hitler gained power in 1933, Thälmann was arrested. He was shot on Hitler’s orders in Buchenwald concentration camp in 1944."
No, that still incorrect. First, KPD, SPD and Centre did not have an outright majority together. Second, it is the Chancellor that is in charge of forming coalitions, they can’t just form a coalition if they had an outright majority anyway in the Weimar system and at no point did Centre try to form a coalition and was turned down by the KPD. The entire point of Hindenburg appointing Franz Von Papen was that he thought that he could convince both the Nazis and Centre to form a coalition with the conservative and monarchist parties. And the reason later to appoint Hitler as chancellor was to form a Nazi led coalition.