My truth: Because of the industry leaders getting arrested during their parties and the war years. And the mount of votes a person running for president got it was soon ceased to exist.
Source: "Dozens of party members, many of them local leaders, were arrested during the war years, and the Socialist Party's electoral performance declined precipitously after 1916. In 1920 Eugene V. Debs, the socialist candidate for president, received only 5 percent of the vote in Oklahoma, down from the 15 percent the socialist presidential candidate had received four years earlier." (http://www.okhistory.org/publications/enc/entry.php?entry=SO001)