as people have and keep pointed/pointing out though (and I'm not adding to the suggestion the other guy made), if NATO or the West just kowtows to the nuclear blackmail, Putin will feel emboldened to keep conquering and killing as he pleases.
It's his biggest card. So regardless of doing nothing or going the violent route, he wins regardless. As you said, he doesn't give a shit, so if he dies in MAD, he'll feel it's a victory if his enemies go down with him.