>>12984552In kayfabe, I believe it was Jack Tunney, the WWF president at the time. He declared the title vacated due to Andre trying to hand it to DiBiase, after Andre "won" it at The Main Event by having an unsanctioned ref count the finish. Then Tunney established the tournament for the world title at WrestleMania IV and gave Hogan/Andre a bye to the second round so they could face each other. Both were eliminated.
I can't recall if WWF officially recognized the title change from Hogan to Andre at the time, but I don't think they ever confirmed it. It was kept intentionally ambiguous to protect Hogan despite him losing the belt. Although today, I think WWF does recognize it as a title change, so today's official answer might be Andre, but that wasn't how it happened back then, or at least it wasn't made clear to the audience.
