3. Braun Strowman wins the Royal Rumble
With Roman Reigns presumably still out of the mix come WrestleMania 35, there are not very many WWE Superstars who could credibly be positioned to challenge Brock Lesnar for his Universal Championship.
Guys like Seth Rollins and Finn Balor could conceivably be put in that role, but have credibility gaps in terms of, if nothing else, their size, and WWE would need to go all in pushing them ASAP. AJ Styles will presumably have had two matches with (and more than likely two losses to) Lesnar in that time. Daniel Bryan would have to cross brand lines, only to face similar challenges to Rollins and Balor, besides no one being especially eager to see him against one of the most physically punishing guys in the business so soon after being cleared from his previous head injuries.
In the end, Braun Strowman is the most likely guy to challenge Lesnar if he is still champion come ‘Mania. Yes, Strowman has lost to Lesnar in four title match scenarios already, but only one of those was a one-on-one bout in which Strowman wasn’t thoroughly protected, and that was over a year ago at No Mercy 2017. There’s reason to believe that the main reason Strowman didn’t win at Crown Jewel was to set him up for the full star treatment in a Royal Rumble win and WrestleMania coronation.