When the world learned last Monday that Fox News host Tucker Carlson had been suddenly and unceremoniously axed by the network with which he had become synonymous, the immediate next question, for me and many others, was: Seriously—why? “Because Carlson was a smarmy xenophobe” is not in itself a sufficient answer to the question. Indeed, those were the traits that had made him indispensable to Fox News. Since assuming the network’s 8 p.m. weeknight timeslot in 2017, Carlson had become the well-coiffed avatar of a brash nativist populism which the host and his staff had deemed “Trumpism without Trump.” This...