Because it wasn’t planned that far. The administration probably thought it would go like Venezuela. A Middle East historian would have told you Iran has building for all our war for decades because it trusts none of its neighbors.

A second problem is that the US knew for a while that we were weak at asymmetric warfare but we didn’t fix it. There was a war game in 2002 (the Millennium Challenge, which was actually set in the Strait of Hormuz) that, though the red team did very much cheat, it did hint at a major weakness that wasn’t resolved.

There are US defense companies today that actually specialize in that but they weren’t given the same attention (but boy are they now).