Russia is winning because it has developed a steady momentum for keeping losses low while attriting Ukrainian forces harshly.

The victory is not by any means a phyrric victory, given that the Russian army is now larger, more experienced and has more material than the start of the war. The Russian economy is also holding up. The only thing that could be phyrric about the war is the loss of life, which is still not too high for russia.

Given the recent offerings, it is obvious that putin does not want to take the whole country of Ukraine. Not only will russia have to pay for the rebuilding, but it will have to face massive amounts of internal resistance for years to come, which is a headache that russia has no reason to deal with as long as they get their demand of no nato membership.

Finally the terms themselves are very generous as I have previously outlined. The loosing side in a war doesn't just get to keep everything with no concessions. That is not how wars work. I have also clearly stated the reasons why a ceasefire now on putin's terms is actually beneficial for Ukraine especially if the war were to flare up again. It would buy them time to recover fighting strength while the Russians would have to unwind their militarization, as maintaining a war economy outside of war would not be taken well by the population.