Louis Menand, in a review of Francis Fukuyama's America at the Crossroads: Democracy, Power, and the Neoconservative Legacy, makes a point about how intellectual legacies get formed:
All the stages of the [neoconservative] movement's development were based on the primitive psychology of the "break"—the felt need, as one ages, to demonize the exact position one formerly occupied. The enemy is always the person still clinging to the delusions you just outgrew. So—going all the way back to the omphalos, Alcove 1 in the City College cafeteria, where Kristol and his friends fought with the Stalinists in Alcove 2—the Trotskyists hated the fellow-travellers they once had been; the Cold War liberals hated the Trotskyists they once had been; and the neoconservatives hated the liberals they once had been. Now the hardening is complete. Neoconservatism has merged with the politics that its founders, in their youth, held in greatest contempt: the jingoist and capitalist American right. We look from man to pig, and from pig to man again; but it is impossible to say which is which.
This helps explain why Fukuyama, instead of writing a straightforward indictment of the war on terror, apparently felt it necessary to present his position in the form of a "break" with neoconservatism—why Krauthammer, an entirely epiphenomenal figure in the creation and implementation of American policy, was the initial target of his indictment, rather than Dick Cheney and Donald Rumsfeld. Krauthammer has ideas; Cheney and Rumsfeld—Fukuyama as much as says so—do not.
Whole article here.
I wouldn't limit the error of the hard break to the neocons. This is what I've always loathed most about born-again seers ranging from Michael Lind and David Horowitz to David Brock to Bill W. and Dr. Bob to Saint Paul. It seems simple enough: Having erred in the past shouldn't necessarily destroy your intellectual credibility, but it definitely shouldn't enhance it. Why should I, who have never been a gutter drunk or a communist or a persecutor of Christians, be impressed by the folly of your youth? Shouldn't that be an incentive to ignore your current nostrums rather than taking them more seriously?
Julian Sanchez burnished the legacy of Fukuyama in a Reason article about his turning away.