One of the major drivers was the Comic Book Store
The world of comics was changing in the 1970s. The fan conventions and the head shops of the 1960s had led to the creation of the comic book store, where readers could buy new & used comics. The comic book store offered a wider variety of comics than newsstands, so readers who might have given up on comics in their teens could read undergrounds and other kinds of books. Through the undergrounds publishers knew there was an older comic book reading audience & the comic book store gave publishers a way to reach these readers. However, the 60s were gone and mature readers were interested in more than tales of sex crazed stoned out hipsters, so publishers experimented with more sophisticated genre tales. One of the first was Manhunter, published by DC Comics by the team of Archie Goodwin & Walt Simonson. Manhunter originally a 1940s hero, was in this incarnation revived by a Terrorist organization to be their assassin. The writing was smart and the artwork inventive. Equally important, the tone was bitter. Manhunter ran as a backup feature in Detective Comics, and was awarded 6 awards from the Academy of Comic Book Arts (the major industry award at the time) for a series 7 episodes long. Although it wasn’t collected in graphic novel form until the 1980s, it was one of the first commercial attempts to tell a completed genre story. The editors at DC comics realized that the time was right for this story partially because of the comic book store clientele. Others followed.
See more about the origins of the graphic novel in my upcoming 2nd edition of “Faster than a Speeding Bullet, The Rise of the Graphic Novel.” Being solicited in comics shops now.
Next: the Trade Publishing Influence