#2. To make him a major underdog
There are two major underdogs heading into WrestleMania, and neither of them happens to be Seth Rollins. This WrestleMania season, the two big underdogs are Kofi Kingston and Becky Lynch.
For The Man, she's had to go up against The McMahon family. Charlotte Flair, a knee injury and more to secure her spot at WrestleMania. For Kofi Kingston, he's going to have to face five other competitors in a gauntlet match.
Either way, he's being portrayed as a major underdog, and that's a good thing because the WWE Universe has gotten behind him organically after realizing just how much he deserves the opportunity.
Having him be an underdog against the authority figures instantly helps people get behind him. Not many people noticed, but Vince McMahon used a recycled term on Kofi Kingston that was once used on Daniel Bryan. He was called a "B+ Player".