Not too strange - the owners of the copyright(/trademark/whatever) for the original Captain Marvel allowed it to expire.
Of course they allowed it to expire because they ceased to exist after loosing a copyright lawsuit with National comics (DC now) because the character was a blatant ripoff of Superman. Then DC bought the Fawcett assets but that was after Marvel made their own Captain Marvel. So Captain Marvel was Shazam, except when he wasn’t, and yeah. Fun stuff. More interesting than any iteration of the character.