Once one person has one, they can tell everyone else what to do unless other people have them, too.

Until we find a way to alter that incentive structure, mutually-assured destruction remains one of our best-available options for tenuous stability and peace.

Why are people so evil...

Perhaps some are, but most people are not.

On the latter subject, I offer the advice of Gandalf:

Gandalf: "You cannot offer me this Ring!"

Frodo: "I'm giving it to you!"

Gandalf: "Don't tempt me Frodo! I dare not take it. Not even to keep it safe. Understand Frodo, I would use this Ring from a desire to do good. But through me, it would wield a power too great and terrible to imagine."

I was always under the impression that the one ring—a weapon so powerful it will corrupt and destroy everything good in Middle Earth—was an obvious allegory for the Bomb.

The point of the fellowship was not to study the ring, make their own, and keep the peace in Middle Earth with a mutual assured destruction. Instead they had the fellowship take the ring back to Mordor where it would be destroyed.

Tolken does not seem to share your belief that: “mutually-assured destruction remains one of our best-available options for tenuous stability and peace”.

EDIT: And neither does the United Nations. I encourage you to read the Treaty on the prohibition of nuclear weapons (and subsequently ask your government to sign it if they haven’t already) and see why the presence of nuclear weapons among our nation states is a terrifying and dangerous endeavor.

https://www.un.org/disarmament/wmd/nuclear/tpnw/

Agree. But some people will see lack of weapons as weakness to exploit. It's easier and higher ROI for 1 to arm, while rest disarm, than for all to remain disarmed, so it will happen. Making the current undesirable state where we have this fantasy of nuclear slugfest, paradoxically more stable.

But yeah, in a sense it's like we're storing AN in a warehouse beside a city. Seemingly stable, but bad if not. Unless we're not storing AN, but just sawdust. But who knows really?

an even more stable situation would be to have every country convinced they have a mutually assured destruction but then for there to be some higher power that can prevent that. so we don't start a war because we believe mad is true but even if we do there's a fallback. but who knows?