Tyler Cowen has written an excellent review of Daniel Okrent's new book, Last Call: The Rise and Fall of Prohibition. Cowen summarizes how the stars lined up in the late nineteen teens for prohibition to occur. One thing he misses, and I'm not sure whether Okrent does also, is a factor that, along with the influences he mentions, made Prohibition easier to implement. That factor is that a milder version of Prohibition was enforced by the federal government during World War I. Robert Higgs, in his book, Crisis and Leviathan, discusses this. Higgs points out that when price controls were imposed on grain during WWI, causing shortages, it was hard to justify using grain to produce alcohol. So the feds banned the use of grain in alcohol.
Also, Cowen misses the public choice aspect of drug prohibition when he writes:
You also need to consider whether drug dealers and users will ever achieve enough social respectability to support a change in regime.
Drug users? Sure. But drug dealers? No way. The vast majority of them want some degree of illegality because, as I have written elsewhere [part of it is quoted halfway down in Jack Shafer's article in Slate], having drugs illegal enhances the return to their illegal skills. This is Bruce Yandle's justly famous "Bootleggers and Baptists" idea.