#2 To establish Daniel Bryan as the mastermind all along
As cool as the idea of a murder mystery or even a whodunit is, one has to remember that ultimately, this is a sports entertainment show and not a crime thriller. Which is why it has to lead to a marquee match that people will tune in to watch. The biggest match in WWE that could happen from this whole scenario is Reigns vs. Bryan.
As Tom Colohue from Sportskeeda reported recently, Eric Bischoff is very high on Daniel Bryan and wants him to get a major push. Which is why it is all too certain that Roman Reigns vs. Daniel Bryan will be the big match coming out of this. It's a certainty that this random individual is not the man behind the vicious attacks.
You cannot put Roman Reigns and an unknown red-bearded man in the poster for Clash of Champions. You can, however, definitely book Roman vs. Bryan.