No leader of a nuclear state is going to initiate a first strike against another nuclear state with a counterstrike capability. What we have here is a modern version of the mutual hostage-taking policy that underpinned peace treaties in antiquity, where the crown prince and other members of the nobility would spend a good chunk of their lives as hostages who would be killed if their king broke the treaty and started a war. Nuclear weapons expand the scope of the hostage-taking dramatically. If Putin initiates a nuclear attack against the US, he is literally killing, via live cremation, all of his relatives and everyone he has ever known, in the American counterstrike. That is why he will never order a nuclear attack against the US. Against Ukraine or some other non-nuclear power, maybe. But definitely not against the US.
No leader of a nuclear state is going to initiate a first strike against another nuclear state with a counterstrike capability.
That is the generally accepted strategy and logic with which I agree.
Moreover, I assess Putin to be a Russian Nationalist that does love Russia and Russians, as authoritarian as he might be, so it's not him I worry about.
I assess Obama and most around him to not love America at all, and themselves above all.
They are true believers.