There could be multiple reasons. You can't hurt russia too much because they have the nukes. Russia can't lose and Ukraine can't win. The deterrence if it exist

There could be multiple reasons. You can't hurt russia too much because they have the nukes. Russia can't lose and Ukraine can't win. The deterrence if it existed should have worked for Russia because America showed to the world that wars can be stopped prematurely and on your terms. This is a moral way to test more weapons on both sides. This war will let all parties know who stands where. This is more like bickering between superpowers and to establish a new equilibrium.