The Conan vogue spilled over into other genres, and fans demanded the oddest combinations. WE want . . . old names of bygone countries that remind us of Conan and LOTR. Magic AND spaceships that look like outboard motorboats. Can you find something, O book publishers?
Sure, we got reams of that crap back in the old pulps. Wait here while we dust it off and give it a new illustration.
That was usually the case, but not here: this was Carter's seventh novel, but the first to be published. That's persistence.
Wikipedia: "Unknown to many of his fans is the fact that Carter was a major scripter for ABC's original Spider-Man animated TV show during its moody, fantasy-oriented second season in 1968-69."