The war was over, and people wanted to forget about it and the past traditions that led to it. It was a period of dynamic economic optimism, materialism and consumerism, which essentially masked some deeper troubling nationalist and tribal movements in Europe, and to some extent in America with its xenophobic and anti-immigration policies. It was also about living in a new modern world, divorced from the old one; Wikipedia says the following about the 1920s:
The Roaring Twenties is a term sometimes used to refer to the 1920s, characterizing the era's distinctive cultural edge in most of the world's major cities for a period of sustained economic prosperity. French speakers dubbed it the "années folles" ("Crazy Years") , emphasizing the era's social, artistic, and cultural dynamism. "Normalcy" returned to politics in the wake of hyper-emotional patriotism during World War I, jazz music blossomed, the flapper redefined modern womanhood, and Art Deco peaked.
Economically, the era saw the large-scale diffusion and use of automobiles, telephones, motion pictures, and electricity, unprecedented industrial growth, accelerated consumer demand and aspirations, and significant changes in lifestyle and culture. The media focused on celebrities, especially sports heroes and movie stars, as cities rooted for their home team and filled the new palatial cinemas and gigantic stadiums. In most major countries women were voting for the first time. Finally the Wall Street Crash of 1929 ended the era, as the Great Depression set in worldwide, bringing years of worldwide gloom and hardship .Such explains the many cultural references in this short clip on the 1920s; some things might surprise you, in particular how much women were free and liberated—a result of questioning of and not being tied down to past traditions. Even so, much of this freedom ended with the Great Crash of 1929. It was too good to be true.
Life is the Roaring '20s, at least how it was for the wealthy and famous. For the rest, it was drudgery as usual.