One of the most immediate reasons for the passage of the Eighteenth Amendment was the Grain Crisis of the First World War. The shortage of this food staple enabled Temperance activists to advocate for limits on the brewing of beers and malt beverages. Herbert Hoover oversaw the Commission for Relief in Belgium during this period. Prohibition became law just after the Great War.
Muchowski, Keith J., "Nexus: The Great War's Grain Crisis and the Coming of Prohibition in America" (2016). CUNY Academic Works.