Jeet Heer explains that Republicans fell for Trump because of years of conservative policy that told them science, reason and skepticism were bad. Put simply, they were primed to be suckers: "It's very possible that I could be the first presidential candidate to run and make money on it."
Conservative ideology, as Perlstein persuasively argues, is particularly vulnerable to grifters because of its faith in the goodness of business and its concomitant hostility toward regulation—which makes it easy for true believers to buy into the notion that some modern Edison has a miraculous new invention that the Washington elite is conniving to suppress. In Perlstein's words, "The strategic alliance of snake-oil vendors and conservative true believers points up evidence of another successful long march, of tactics designed to corral fleeceable multitudes all in one place—and the formation of a cast of mind that makes it hard for either them or us to discern where the ideological con ended and the money con began." There's another factor at work here: The anti-intellectualism that has been a mainstay of the conservative movement for decades also makes its members easy marks.