Before copyright, storytellers sharing and reusing characters, settings, and plots was the norm. It’s the way humans evolved to tell stories, over tens or hundreds of thousands of years. We instinctively want to hear stories about characters we know, and to see new twists on familiar tales—“shit getting weird” is the point. It’s why franchises, fan fiction, and adaptations are so popular.
And copyrights were never intended to protect the work of artists—they were first introduced after the invention of the printing press to censor subversive works being written for a newly-literate public, and quickly evolved into a means of creating monopolies for commercial printers. Writers were eventually given a stake in order to create a new rationale for copyright laws after they were suspended due to public backlash—but that was a minimal concession by the real commercial beneficiaries, not the main purpose.