To be fair, they just happened to be the only ones with nukes at the time. Someone had to try it sometime to figure out exactly how horrible it would be.

It’s much preferable that it happened with a 20kt bomb, as opposed to a 20Mt one.

Interesting point: nobody has used a fusion bomb in a war.

It was threatened this week, though. I don't think that has happened in a long time.

in using the rules-based order (its right to threaten people with nukes) to break this rules-based order

In the way they actively threatened a nuclear holocaust.