Temperance organizations had existed for more than 100 years before the Volsted Act was passed, all of them trying to get attention to the damage done to families by alcoholism. But these groups ( like the Women's Christian Temperance Union) also had other progressive items in the agenda, like abolition of slavery, and votes for women. Politicians knew that they could be against banning the sale of alcohol but progressive on other issues and still get support from these groups.

That changed with the Anti-Saloon League and it's leader, Wayne Wheeler. The ASL had one issue, and a politician either signed on or the ASL would support his opponent in the next election. The ASL also got the support of many churches, created parades of beautiful young girls in white demanding action....With other temperance groups joining in, the pressure on politicians was enormous.

On the other side there was much less organization. The groups to lead it- brewers and distillers, saloon owners, Lutherans, many Catholics- couldn't unite and rally the way the Temperance forces rallied, and couldn't formulate a good answer, or apply equal political pressure. The result was an initial victory by the ASL and related groups. The problem with that victory, however, was that it was only political, not popular. A referendum in 1920 would have shown that a great number of people drank, didn't think they had a problem with drinking; likely a majority. As a result, the Volsted Act was greeted with massive non-compliance. Most people figured out a way to keep drinking. Where there's a market, there will typically be a supply, and in this case the supply was illegal. That began to make Prohibition look not only ineffectual but a huge opportunity for crime, with gangsters running rampant. In 1931 Franklin P Adams would write a short poem satirizing the Temperance line:

Prohibition is an awful flop.

  We like it.

It can't stop what it's meant to stop.

    We like it.

It's left a trail of graft and slime,

It won't prohibit worth a dime,

It's filled our land with vice and crime.

    Nevertheless, we're for it.

When the Depression hit, it was also easier for the opposition to point to the economic benefits of breweries, and the fairness of the poor working stiff being able to drink a beer.

In the end, it was a perfect example of the limits of single-issue advocacy.