I suspect the Comics Code was also a factor. With its adoption in 1955, comic book writers could no longer rely on the old staples of brutal gangster violence, homicidally mad villains, Nazi scientists performing experiments on the unwilling, and other dark plot devices. So it's little wonder that writers soon turned to the fantastic (bizarre SF adventures and endless transformations of superheroes into gorillas, fish, monsters and whanot) or to goofy, domestic comedy-type stories (Superman marries Lois! Superman marries Lana! Batman marries Lois! Lois marries Lan--well, not that last one.)