McNamoron sold Congress on the lie that conventional warships were more cost effective than nuclear ones, because he was obsessed with proving his stupid, "transformative" ideas were always better than anything anyone else said and no amount of factual reality would ever convince him otherwise. His so-called "whiz kids" very quickly learned that their actual job was simply to package whatever McNamoron had pre-determined to be the winning idea so that it didn't look like an arbitrary snap judgement. Unfortunately, they were very good at doing so, and Congress bought it hook, line, and sinker.
Before McNamoron's lies started getting entrenched -- yes, Congress cancelled a few very expensive nuclear ships, but those were factually justified cancellations of technology that legitimately didn't work, and they did (however reluctantly) in fact fund a full array of nuclear-powered frigates, destroyers, cruisers, carriers, and submarines.