I wouldn't cut things off at a half decade. A little more than a decade prior the German communist leadership were killed by military companies in coalition with the SPD, and then those same military groups tried to overthrow the SPD government, but the SPD ended up compromising with the coup uprising anyway.
So understandably the extrajudicial slayings of German's communists sort of formed a schism between the SPD and the KPD. This all but assured any remaining communist power or authority in Germany had to look to the barely formed USSR for support: they'd literally fled there with their lives.
The important context is this period includes the aftermath of World War 1 where the German Empire collapsed and with the loss of centralized government and authority, communes and provisional governments were being formed all across Europe. There were also mercenary groups wanting to abolish the Republic and restablish the monarchy.