For many of us who have studied, deeply, the works of Adam Smith, J.S. Mill, Hayek, von Mises, Sowell, Mankiw, Garrison, McCloskey, and others with Austrian and Classical Liberal theoretical underpinnings, the death of the intellectual movement began when intellectually skilled yet stupid people like Charles Murray (The Bell Curve) were given credence by the Republican and Libertarian Parties.
The Religious Right wasn't seeking religious liberty. It was, often, seeking a cover for hateful biases and a desire to legislate morality. Religious men and women led the Abolitionist movement and the Civil Rights movement, but those aren't the people of the modern religious GOP subset.
We let racists, nationalists, sexists, and worse claim the banner of "personal liberty" and "states rights" when we should have been and must today reject these people. Horrible people have used libertarian and classically liberal ideals to defend their twisted opinions and hatreds.
The Libertarian Party has never understood Smith, Mill, or Hayek. The GOP long ago turned against the ideal of the sovereign self promoted by Mill (as did the Democrats, in different ways) by legislating morality.
Adam Smith feared a classical liberalism without a moral and ethical compass. A movement that didn't actively promote meritocracy and punish fraud, greed, and manipulation. Smith opposed rentiers, proposed progressive tax rates, and suggested the pursuit of personal knowledge was the highest good. Mill wasn't about building wealth, either. On Liberty is about being left alone to do whatever you want, even if you aren't great at it and won't be wealthy. On Liberty is about individual freedom to succeed or fail, to do what you want with your body and mind.
I'm tired of the caricatures other people post about classical liberalism, utilitarianism, and libertarianism. We have allowed this to happen, though, by not standing up and demanding, loudly, that others reject men like Donald Trump.
Trump is the natural culmination of movements that did not roundly reject the greedy, racist, nationalist nonsense of "thinkers" like Murray and others.
We let this happen.