When the alternative may be "global nuclear annihilation" there is a chance that that is actually the best choice, particularly as he appears to have serious health issues and as such may die soon.
Don't know about you, but if someone has a knife or gun to my throat they can have my wallet and phone. Whereas if they just threatened me with their fists (analogous to conventional weapons) I'd possibly fight back.
Well, it is, because we could put boots on the ground and planes in the sky. But that's then WW III, which Putin may take nuclear, and then we all die. The latter is a "worst possible" outcome which must be avoided at all costs. Even Putin taking over the whole world (which isn't going to happen) is less bad than that.