#1 Roman Reigns is the hero in this story
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In many cases, WWE cannot turn a Superstar heel because of the story they want to tell. The biggest example is Roman Reigns, who has been pushed as a heroic babyface despite some nasty reactions in the past. Those shackles are off for Goldberg.
Funnily enough, Roman Reigns being the hero of this story allows WWE to book his opponent to turn heel. Babyface vs Babyface matches don't usually work, unless there is at least one Superstar who is insanely over with the crowd, like John Cena vs The Rock and Shawn Michaels vs The Undertaker.
In this case, Reigns is not universally loved, especially since it's in a world title match at WrestleMania. If Goldberg turns heel, the alignments are locked in and the Big Dog becomes the clear hero. Hopefully, this would get more of the crowd behind him at WrestleMania.
He is going to win the Universal Championship at WrestleMania, so why not book him to conquer an unstoppable evil monster in the process? One that everybody would want to see lose, no less.
If Goldberg turns heel for this program, everyone wins. But the biggest winner might be Roman Reigns himself, not only from the championship perspective.