Nuclear saber rattling has been the norm for a very long time; it's just that after the fall of the Soviet Union there wasn't much need for it. Things have returned to their more traditional state.
Putin has been doing it since at least 2014 (along with the more conventional though due to nuclear deterrence more ridiculous threat of "visiting Berlin again").
It's just that until last month it was taken as just posturing to remind the West and the Russians that Russia, as a nuclear power, has to be taken seriously.
