Complex sentence: By the 1920s the circus was declining as a major form of amusement, due to competition such as amusement parks; movie houses and burlesque tours; and the rise of the radio.
Split into simpler sentences: By the 1920s the circus was declining as a major form of amusement. We began to see competition such as amusement parks; movie houses and burlesque tours; and the rise of the radio.