So Republic Pictures chose "Captain Marvel" instead. DC was obviously not pleased. Fawcett had already published "Master Man," an obvious copy of "Superman" that they stopped publishing after DC ...
The first superhero movie ever was based on a DC character, who years later caused huge legal issues with Marvel, and was eventually renamed.
Superman and Shazam have a long history in the comic book medium, with a new theory revealing how their first comic cover appearances are connected!