Trump’s inability to comprehend the relevance of Persian Gulf supplies to American motorists may explain how he stumbled into his Iran war in the first place. A threat to the Strait of Hormuz may be the most war-gamed problem in the whole U.S. military inventory. It’s thorny enough to have deterred American presidents from attacking Iran for nearly 50 years, no matter how provocatively Iran behaved.

And this is some statement.
Does Frum really believe that nobody understands the oil market? Sheesh already. This is just more backwards-looking navel gazing.

For the Administration to be prepared for it, they would have had to have the resources in place to counter that threat - either our own resources or to have invested the appropriate diplomatic resources to get the resources of other nations available - and they would have had to be in a position to use those resources.

Oh, so we have another 50 Burke-class destroyers, or we went back in time and bought the FREMM ships from Italy?

(We didn't do that)

Which seems like a pretty poor tradeoff for simply getting new younger mullahs in charge of the same radical Islamic authoritarian regime and taking out their air force and navy, along with using up a lot of our inventory of interceptors and tomahawks in order to reduce their inventory of ballistic missiles.

Maybe. Maybe not.
You're overlooking the fact that Iran had ballistic missile capabilities (multistage) that were unknown before. Even Mossad evidently didn't know that they could range out over 4,000km. And if you can build a two-stage rocket that can go that far, you can work on a 3-stage rocket capable of hitting the US. Then throw in their 60% enriched uranium.

I'm amazed at the number of people who really don't believe the Iranians wanted the bomb. It's just head-scratching.