Putin et al are not in Moscow but dug somewhere deep probably in Ural mountains. This alone tells you how Putin thinks and how safe he feels. Now I don't think that Russians ever did dig deep enough to avoid evaporation from few megaton warheads hitting such place in quick succession, but not sure if Washington knows the exact location.

Anyway such attack would prompt similar ICBM response, they are generally quite incompetent as we can see in Ukraine, but not that incompetent to not have this working.

And nobody in west is going to justify killing few million civilians in Moscow, our society is well beyond that point.