Zumwalt was a bit of a maverick, like Rickover but perhaps less abrasive. Anyway, look at drones...those had to start small...air jockey's understandably not fond of change that takes a man out of a machine...and to the point where a human should be making ultimate decisions on lethal execution there is a good point there not to lose sight of...so our tech advances largely skipped over advanced missile tech beyond the standard array deployed for decades.
That and I don't know, cockyness, hubris...self-delusion the REMFs didn't think it was needed or manageable given the usual appetite for toys they like and want.
Given expertise, it shouldn't be that hard to catch up in hypersonics, but I do not think the current batch of boot-licking REMFs is capable of focusing on the project given the many demands and distractions they are responsible for from drag queen hour for the troopers kiddies to throwing weapons and ammo away in the black hole of Ukraine.
We can sum this up to the broader DeepState/DemoCommie/Cuck total fustercluck and complete shi!tshow SOP's we've come to know and despise.