"Following the failure of the uprisings Levi was expelled from the Communist Party for publicly criticizing party policies in his pamphlet Unser Weg. Lenin and Trotsky substantially agreed with his criticisms, but not the way in which he had made them. Lenin sent him a private letter through his friend Clara Zetkin, in which he asked Levi to accept the expulsion for "breach of discipline" and then adopt a friendly approach towards the KPD and cooperate with it in the class struggle in a loyal manner. If Levi would do so, Lenin would then push for his reinstatement in the party. Levi did not accept this proposal and continued to criticize the party sharply and condemn its leaders. This led Lenin to revise his previously still favourable attitude towards Levi"
what do you expect from, even radical, social democrats? More seriously it was probably both because the spd at the time was brutally crushing leftists, so you wouldn't want to get it on your bad side which meant that the communists were marginalized and throwing hail marys after hail marys, not a very appealing prospect to lead to change, and that the spd still had power at that time and there must have been at least some brainworms in the form of "but we can change it from the inside"
Every time I read about the SPD in the early 20th century, I become more convinced that time is a flat circle. :marx-goth:
In an infinite universe anything that has ever happened, that ever will happen, has happened already and will happen again and again forever.
Which is just one of the many reasons why we need to kill god.