> Because, IMO, Russia would be destroyed the first time they threatened NATO.
Maybe. Or maybe the big powers might realize that sending hundreds of thousands or even millions of people to die in an all out war (depending on how big it gets and who else gets involved) is a harder sell than settling on appeasement and so smaller states would lose their sovereignty.
I live in Latvia. If there's no risk of MAD, then what's to prevent some opportunistic Russians from invading my country and seeing whether NATO would actually do something about Article 5? Some are pondering whether that's not a direction that Russia could move in even now - stage something relatively small and see how NATO responds. They're already regularly violating our airspace and doing cyber warfare against us and trying to drum up opposition to our government (as flawed as it may be) by the ethnic Russian people.
We (I'm an American) have four ballistic missile subs that no longer carry ballistic missiles because of arms reduction treaties. The subs still exist, though, with each of the Trident launch tubes instead holding 7 Tomahawks. They are built to hide and they're very good at it--we can't even reliably track them ourselves. That means they could sneak in to launch points some distance from Russia. The Ukraine war has shown that heavy air defenses sometimes work against ground hugging missiles (but remember the Moskova--despite fearsome anti-air capability it for some reason couldn't engage two sea hugging missiles), but ares without heavy defenses fare poorly against even crude low altitude stuff. Expect most of those Tomahawks to get through, and there goes Russia's logistics capability. Most stuff of importance is within Tomahawk range of the coast.
That's why global nuclear disarmament seems only slightly more plausible to me than (e.g.) global artillery disarmament. For the foreseeable future there are going to be some nations that see nuclear weapons as the more affordable (or the only affordable) deterrent against rival nations that can field much larger armed forces.
Because, IMO, Russia would be destroyed the first time they threatened NATO.