#1 Adding some Star power
No matter how much fans want the company to give Kofi his moment at the show of shows, the fact remains that WWE doesn't trust Kofi as a main event player.
He has been treated as a comedy character with his New Day gimmick since 2014. The only reason WWE changed their Mania plans was to cater to the WWE Universe. But that doesn't mean that WWE would want to put all their eggs in the same basket.
A singles match between Daniel Bryan and Kofi Kingston doesn't scream a star-studded affair. Hence, WWE will insert a white-hot returning Owens into the match, to give the match a big-time Mania feel.
Owens' update promos have been received well by the fans, and his return on SmackDown was met with a sea of loud cheers, signifying the fact that Owens is more over with the fans than he ever was. His inclusion in the match will be a much-needed boost to the star power of the bout.