A single Tomahawk missile could obliterate Moscow which would immediately end the war because Russia is extremely centralized. It's the reason almost 80% of all Russian SAM capability is stationed around the city.
Putin is unpredictable but he's not stupid. You don't become president of Russia by being stupid.
Do you even know how big Moscow is? And nuclear Tomahawks were discontinued. Even if they weren’t, you’d need dozens to obliterate Moscow.
Who attacked Ukraine, again?