The most accurate analysis of why the Russian Soviet Federated Socialist Republic (RSFSR) was the most powerful Soviet socialist republic in the Soviet Union is: The Russian Communist Party and the head of the government ran the state from that location.
This reflects the political and administrative significance of the RSFSR, as it was the central hub of power in the Soviet Union where key decisions were made, influencing the entire federation. While size and military conflicts may have played roles, the centralization of power in Moscow was the primary reason for the RSFSR's dominance.