The war can’t end if people see Moscow as having lost on the battlefield to tiny Ukraine.
Moscow could settle for less territory if at the end of the war, vast numbers of Ukranians were seen at the point of slaughter begging for their lives.
The reality is Russia was fighting NATO, and the “result” of the war - win, loss or tie, plus territorial arrangement and the Constitution of Ukraine - needs to favor a stable strategic balance between the two powers.