How did WWI change Progressivism?

The Progressive Era is generally said to have ended with
WWI.  So the answer to your question would be that World War I essentially ended
Progressivism.

After WWI, the US entered an era that is
generally known as "the Roaring '20s" and is said to be the time when the country
enjoyed a "return to normalcy."  During the 1920s, the country moved away from the
reform spirit that had motivated Progressivism.  In place of that, there was simply a
desire to have political peace and a desire to enjoy everyday life.  These desires are
said to have ended Progressivism.