This still relies on humans carrying out these orders, which, historically, they have never done (Cuba Crisis, false alerts in the USSR). Putins button isn't wired to the ICBM launcher.
I don't think the button was ever pushed. Cuba crisis came very close and the false alerts were automated messages that were correctly deemed as false by the commanders. As far as I know there has never been a direct order to fire that got denied.
Yes, but it still comes down to the fact that it is at least unlikely for the entire chain of command down to the person who launches the nukes to look in the eye of the annihilation of society as we know it and still advance/carry out that order. In every situation where humans were faced with an order to launch, they decided not to carry it out so far.
I have a different interpretation of those close calls: we were very very lucky and should not rely on defiance as a mechanism to avoid the apocalypse.
I've seen an interview with a former CIA spy who used to work in the bunker where they would have to insert rings (two of them) if an order came that said to launch nukes. They preselected them all on a psychological profile and, importantly, they did drills that they didn't know were drills. So they never knew whether the command coming in was real or not. They "launched" every single time.
I can very well imagine that this kind of "loyalty" would be tested in Russia as well.
That also raises the question of how many of Russia's nukes are still viable, and how many of their ICBMs will work properly. There is also the factor of how effective the anti ICBM system that America explicitly does not have in orbit would be. 🤔