The Death of Superman

The story of The Death of Superman's conception goes back to the 1985 crossover Crisis on Infinite Earths. Following that event, DC Comics rebooted their continuity and relaunched the Superman character with the miniseries "The Man of Steel", written by John Byrne. However, due to disputes with DC, Byrne left the Superman books and was replaced by Roger Stern. While the stories continued from Byrne's revamp, sales slowly dropped. In an effort to attract female readers, the Lois Lane/Clark Kent/Superman love triangle, in place since 1938, was changed. In a development based on events in Byrne's revamp, Lois was already falling in love with Clark Kent, rather than with Superman. In a story arc titled "Krisis of Krimson Kryptonite", Clark proposes to Lois; she accepts. Although the road was set for the marriage of Lois and Clark, an unforeseen event would change these plans.
Viacom had cancelled the Superboy television series produced by Alexander Salkind (Salkind produced the first three Superman films starring Christopher Reeve, as well as the Supergirl movie). Warner Bros., the owner of DC Comics, created their own Superman television series, Lois & Clark: The New Adventures of Superman, premised upon a romantic relationship between Lois Lane and Clark Kent/Superman. One of the ideas that arose during production was the wedding of Lois Lane and Clark Kent/Superman. Warner Bros. learned that DC Comics was planning a similar plotline in the Superman comic books, and as a result DC, Warner Bros., and the Superman writing staff came together and reached an agreement: the Lois and Clark wedding arc in the comic book would be put on hold, to resume once the Lois & Clark TV show reached its wedding episode.
With the original storyline set aside in the comic, an original event was needed to replace it. According to a documentary on Superman: Doomsday, the Superman writing team members were miffed at having a year's worth of story planning put aside, and flustered for ideas. At the end of one meeting, Adventures of Superman writer Jerry Ordway suggested, jokingly, "Let's just kill 'im." The joke became a running gag in story meetings, but eventually gained traction with Superman group editor Mike Carlin. In the documentary film Look, Up in the Sky! The Amazing Story of Superman Carlin states: "the world was taking Superman for granted, so we literally said 'let's show what the world would be like without Superman'."