Russia leaves Ukraine the war is over, its that simple. Not sure who in the West wants a war that is costing everyone billions, but maybe you have a theory?
From a historical perspective the Western European countries and the USA were quite content to let Russia have what it had taken by force of arms by 2014. Those were small territories with Russian speaking populations and while in violation of the post WWII no changes in borders by force e.g. the peaceful reunification of Germany, did not result in a change of governments or formal borders. The 2022 invasion of Ukraine with Russian forces marching on Kiev, Ukraine's capital, signaled an overthrow of the government and the de facto incorporation of Ukraine into Russia. Even for the German doves that was a step too far as it upended the post WWII agreements about borders etc as previously noted. That had to be stopped before Russia attacked a NATO country, Poland comes to mind, and NATO had to go to war.
After WWII the German populations in various countries were removed as they had aided and abetted the Nazis. Other than Austria, which was effectively neutered, all Germans populations were removed. When Russia loses this war the same thing is probably going to happen to Russians, there will be an ethnic cleansing as no one wants a fifth column in their country or an excuse for Russia to invade by claiming Russians are ill treated.