#1 To play the whole Phenom vs. Phenomenal angle
As lame as this reason may sound, matches have happened in WWE for reasons that were far lamer. I mean one of The Undertaker's most recent big feuds was based on whose yard it is anyway, with Roman Reigns.
Essentially Vince McMahon will need a sales pitch for WrestleMania and a match between The Phenom and The Phenomenal One has a fantastic ring to it and even lapsed fans can gravitate to it. It does not need any more explanation than this- one of the two men is an undead zombie while the other can do things in the ring that most people alive cannot.
But all said and done, who would have ever thought that AJ Styles, the heart and soul of TNA and one of the most promising Cruiserweights in WCW would be rubbing shoulders with The Undertaker someday? I certainly didn't.
How cool is it that such a match can potentially happen at a stage like WrestleMania 36, and what an honor it would be for me to review it for Sportskeeda!