In the 1980s there was a realization to start creating comics that would be attractive to the aging readers. With new writers such as Frank Miller, a darker influence began. The first sign of this change was the Dark Knight Returns. In this graphic novel, Batman who is much older, fights his old foes in a different way. The fact that Bruce is older in the comic is a definite attempt to reach out to the older readership. In addition the way Batman was depicted was very dark. This was not the Batman from the Adam West era. This was a rebirth of this hero from his beginnings. This probably was the only way that Batman could have survived. It can go without saying that the Batman from the 1960s could not have survived in the 1980 environment.
Over the course from the conception of the Superhero, to the 1980s, comics have developed severely. What was seen in the 1980s was a change from the days of the comics code. By not having abide by the strict rules, comics could be darker and more violent. This is shown when the joker begins to brutally murder innocent people in the Dark Knight Returns. All in all there are many different factors to why comics seemed to be darker than before. Due to a combination of an aging audience, and a freedom of writing more adult situations, comics became more violent and outspoken.