Complex sentence: In the late 1940s, the popularity of superhero comics waned, and in an effort to retain readers, comic publishers diversified into other genres such as war, Western, science fiction, romance, crime, and horror comics.
Split into simpler sentences: In the late 1940s, the popularity of superhero comics waned. In an effort to retain readers, comic publishers diversified into other genres such as war, Western, science fiction, romance, crime, and horror comics.