During the twenties, menswear experienced a significant progression.
The pre-World War I, Victorian, conservative suits of the past gave way to more masculine suits, each fitted to the wearer. Before, men had worn structured, slim “sacque suits.” These suits were made of uncomfortable fabrics, and could be unflattering on the body: narrow shoulders, short sleeves, and uncomfortable trousers.
The twenties saw an increase in the “fashion conscious” of men, a result of increased standard of living and consumerism. Like the women, men saw film stars (such as Rudolph Valentino, Charlie Chaplin, and Douglas Fairbanks) sport looser, baggier pants, fuller shoulders, and new hairstyles and attitudes. These trends were emulated by the male population, as men adjusted to an attitude of fashion forwardness.
(Sources: www.1920s-fashion-and-music.com, fashion.tahkautka.net)