Russia knows that time is on its side. It can just pause enough to rearm and then attack again. What will we do differently then?
Plus, at some point Russia will start using nukes and then we will be forced to back down. We are not going to blow up the world to save Ukraine.
Russia has a greater population, but has been relying largely on conscripts among the poor, the incarcerated, and third world nations likes North Korea. Thats a resource that is far smaller in number than their total population. As soon as it’s tapped out, they either have to give up are start conscripting people in the middle and upper classes, and that will turn the Russian population on the war and their leaders faster than anything.
In this war the only winners are US/EU weapons manufacturers, there is no winning scenario. Something Trump cannot understand and Putin cannot accept.