The best 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 response highlights the central political authority and administrative control that the RSFSR held within the Soviet Union, which contributed significantly to its power and influence compared to other republics. The concentration of governmental functions and the leadership of the Communist Party in the RSFSR made it the core of the Soviet state.