Their deaths easily left a power vacuum that was filled by soviet leaning german communists, most especially after 1922 when the civil war ended and the soviets emerged victorious. While some of the prominent german communists that werent russian soviets… were dead.

Yet the period of the United Front between the KPD and SPD lasted from '23 to '28. The idea that it was an organic change because of deep-seated grudges is extremely questionable even just by the timeline, much less the details of the interactions of the 20s and early 30s.