The author Lois McMaster Bujold has said that “the writer should always reserve the right to come up with a better idea.” That's a useful guideline for any reader to keep in mind. As any long-form story evolves, it usually picks up a few dead plot branches or abandoned characters, because the author can exercise their option to drop what they're doing for any (or no) reason. Sometimes it's not a continuity error; it's a deliberate change in direction.