Suomifinland
Central Defender
Because it's not based on one man. If we nuke him personally they have submarines who will be ordered to strike back immediately. Its not a case of "kill Putin and kill Russia". And launch sites everywhere. Also it's unlikely we could take out every land based nuke site, that's just the ones we know of.
Furthermore, if they detect a launch or multiple launches as would be the case under your plan, they will respond in kind before anything hits them, ensuring both sides are wiped out
They have a system called Dead Hand or Perimeter depending who you believe that is an auto retaliate if leadership taken out.
If only it were that simple eh?