Having an Amendment prohibiting "the manufacture, sale, or transportation of intoxicating liquors within, the importation thereof into, or the exportation thereof from the United States and all territory subject to the jurisdiction thereof for beverage purposes" stated the general intent of the government, and so gave the government broad powers in defining what was to be banned, and also gave it broad powers for creating laws specifying enforcement, penalties, etc. It was somewhat vague, really. Many people thought that "liquors" would only be distilled spirits, and were surprised when beer and wine were included in the Volsted Act that enforced the Amendment.

But yes, it is astonishing that the 18th Amendment passed so quickly. It was the outgrowth of a moral crusade that identified alcohol as the cause of many of the social problems faced by the US in the later 19th c. ( a much easier target than, say, low wages: and with no organized defenders). It was also the result of the success of the first single-issue advocate, Wayne Wheeler, president of the Anti-Saloon League. Other Temperance groups would endorse political candidates who were not Dry but progressive in other matters. Wheeler's ASL required politicians to sign onto the ASL's platform or it would endorse their opponent. No senator, governor, etc. wanted to oppose Wheeler, and the result was a political tidal wave. But after it was put into enforcement with the Volsted Act, Prohibition turned out to have weak popular support and enforcement became impossible. Remarkable for how fast it was ratified, the 18th Amendment is also remarkable for how fast it was repealed.