How did World War I see progressivism at the zenith of its influence yet also cause its eclipse?

Woodrow Wilson decided to involve the U.S. in World War I to "make the world safe for democracy." Wilson, a Progressive, wanted to create a League of Nations that would prevent wars by disarming combatants and relying on countries to provide security for other nations. Wilson's goal of achieving world peace was the zenith of progressivism; however, Republicans in Congress challenged the League of Nations, and the U.S. was not a signatory to the League.
After the U.S. became involved in the war, progressive goals were not achieved, and the cause was largely lost. For example, after the Russian Revolution of 1917, the U.S. was deeply afraid of communism and anarchism. Communism was denounced in the popular culture and the American media as representing un-American ideas, and many foreigners were believed to be sympathetic to anarchism and communism and therefore unwelcome in the country. This was particularly true of Italians. In the 1921 case of Sacco and Vanzetti, two Italian immigrants were accused of a robbery in Massachusetts and executed in 1927. Historians still debate the innocence or guilt of Sacco and Vanzetti, but there is no doubt that anti-immigrant and anti-anarchist sentiment played a role in their trial and sentencing.
In response to the fears surrounding communism and anarchism, Wilson passed the Sedition Act of 1918, which cracked down on the expression of anti-government opinions. During the "Red Scare" (another iteration of which occurred after World War II), Attorney General A. Mitchell Palmer conducted raids on people suspected of being radicals. Others were deported, and these actions were unconstitutional in nature, as raids were conducted without warrants and citizens were jailed without the right to counsel. The war wound up resulting in the abridgment of people's rights and the eclipse of the progressive cause as the 1920s brought about a return to political conservatism.