If that Russian oligarch is deluded into believing MAD is now obsolete due to some top secret technology or military maneuver or whatever than all bets are off
That's what has been causing more tension than the actual nukes for a while now - effective countermeasures, or ICBM countermeasures. If one party has an effective countermeasure against ICBMs, it takes away MAD and the one holding the countermeasure gets to claim military superiority.
Of course, I don't believe there is such a system, or if there is it's very local; if it comes to nukes, they will come from anywhere (e.g. nuclear submarines) and can end up anywhere. If there was an effective anti-nuke system, we'd see launchers pop up everywhere, or if it's a space based one, see many launches of those to get enough coverage (like starlink).
I think fear of countermeasures unbalancing MAD is also what’s driving development of Russia’s non-ballistic missile based warhead delivery systems, like status-6 [1].
I doubt it. I really don't think he would choose a nuclear option, but rather an option in which his Russian troops fight NATO to the very end, something like Japan in the end of WWII. Except that this time, we can't use nukes.
