In the early '70s, Marvel Comics put out a large number of horror comics to cash in on the broader latitude granted by some revisions in the Comics Code. The resulting titles included new interpretations of traditional monsters like Tomb of Dracula (probably the best of the bunch) and Werewolf by Night, but also new supernatural superheroes like Son of Satan and Ghost Rider. At times—and particularly in Ghost Rider's case—it seems that Marvel was stretching to squeeze in supernatural elements, and to test the limits of what the revised Code would allow.
Take, for example, the origin story of Ghost Rider, as presented in his first appearance in Marvel Spotlight #5 (Aug. 1972) by Gary Friedrich and Mike Ploog. Johnny Blaze is an orphan being raised by a family of motorcycle acrobats. When his adoptive father, "Crash" Simpson, is diagnosed with an unspecified terminal illness, he does what any mixed-up-orphan-being-raised-by-a-family-of-motorcycle-acrobats would do: he invokes the power of Satan. (No, really.) The occult element, arriving seven pages into a story that has made no reference to the supernatural, comes completely out of left field. It's a jarring shift, and has more in common with Jack Chick than Jack Kirby. But lest you think that Marvel is endorsing such Hammer horror theatrics, we soon learn that (surprise!) Satan is very, very bad and can't be trusted. Because of his lack of occult legal savvy, Blaze is cursed to transform into the skeletal Ghost Rider at night to serve as Satan's envoy on earth. As is often the case with sinister-origined superheroes, this ceased to be a bad thing in time. Blaze gained increasing control over his supernatural form. The character ultimately ceased to be a messenger of Satan going to and fro on a Harley, and settled into his role as a fairly straightforward, Evel Knievel-inspired superhero.
It's a bit difficult to say what the religious content of Ghost Rider's origin actually means—it's a story so random, it's tough to pick follow the thread of any themes (beyond, of course, the theme of skeletons on flaming motorcycles looking cool). I suppose it's a story about hubris and the tragedy that can result when we don't accept circumstances beyond our control. But in the end, Johnny Blaze himself puts it best—the devil's got a lot of gall.