Why the Eighteenth Amendment?

Why does the Eighteenth Amendment exist? And no, I am not referring in any way to the numbering: it is obvious that the next amendment to the U.S. Constitution after the Seventeenth would be the Eighteenth what ever it was about. What I am asking is, why was the prohibition of alcoholic beverages an amendment, making it part of the highest law of the land? Why didn't the temperance folks just get Congress to pass a law prohibiting the manufacture, sale, transportaion, importation, and exportation of alcohol?

Reading several articles about prohibition on the web did not answer this question. I believe, though, that the answer is evident if one reads the U.S. Constitution and thinks about it: Prohibiting the manufacture, sale, transportaion, importation, and exportation of anything was not a power given Congress! It would seem that Congress, recognizing that fact, did the only thing that they could do to satisfy their constituents, which was to propose an amendment to the Constitution granting that power. This was then followed by the legislatures of 36 states ratifying the amendment so that they, too, could satisfy their constituents.

Unfortunately the understanding of the U.S. Constitution on the part of Senators and Congressmen since has gone down hill more and more. This has resulted in Social Security, Medicare, drug restrictions and prohibitions, and many other laws that exceed the authority of the Federal Government. These things should rightfully be the province of the governments of the several states. This includes health care. Our leaders had enough intelligence, wisdom, education, and integrity to do things right in 1917, it is a shame that they do not now.