Neoconservatism went out of fashion because the neocons pushed for wars that killed hundreds of thousands of people in the Middle East, and completely destroyed

Neoconservatism went out of fashion because the neocons pushed for wars that killed hundreds of thousands of people in the Middle East, and completely destroyed the region for nearly two decades (and counting). American actions during this period severely undermined the international legal order, violating prohibitions on wars of aggression, torture, and assassination.