>> But in reality, all it takes is a mistake or a madman to set off nuclear armageddon.

> The works us a lot more interconnected and interdependent. What would Russia be without the west to export its oil and gas to? What would China be without foreign markets? We all need each other.

The argument was "all it takes is a mistake or a madman." Neither cares about the fact that "we all need each other."

If you worked anywhere in tech long enough, you should be aware how much unexpected errors are indeed possible even in "old and tested" workflows.

And some madman is always somewhere where "everybody thought he's so nice."

> A limited or regional nuclear exchange would be catastrophic, but not species killing.

Note: "species" and "civilization" aren't the same.

OK, what is the scenario where a single madman causes a complete simultaneous nuclear conflagration by the USA and USSR, the only countries with enough bombs to cause a global nuclear holocaust?

Russia and the USA have no interest in destroying each other. All the other nuclear powers are too small fry to cause more than regional damage.

> what is the scenario where a single madman causes a complete simultaneous nuclear conflagration

An actual nuclear war planner wrote a whole book about that:

"The Doomsday Machine Confessions of a Nuclear War Planner"

https://www.bloomsbury.com/us/the-doomsday-machine-978160819...

P.S. USSR doesn't exist anymore.

There is certainly less of a threat. But imagine what a small fraction, say a few dozen thermonuclear bombs, a couple SLBM's worth, would do to major population centers and the economies they power. That and the after effects would be enough to call the continued viability of modern civilization into question.

Nuclear weapons remain the surest way to end civilization on this planet, and the chances of that happening are far higher than, for example, a meteor strike.