#3 The build to this match has been inadequate
Love him or hate him, one cannot deny that Brock Lesnar has been consistently presented as a HUGE deal in the WWE. Just look at his list of accomplishments. Beating him should be a star-making moment.
Only five men have defeated him since he returned to the WWE. Even the great Randy Orton failed to defeat him. Moreover, only one relatively newer superstar, Roman Reigns, has defeated Brock Lesnar. The rest were all established mega-stars. Even Roman Reigns failed to defeat Brock Lesnar on four occasions before finally prevailing.
So the question is this - is the WWE going to have Brock Lesnar lose his Universal Championship to a replacement challenger in a match that has had two weeks worth of build up? Or will Brock Lesnar lose his Universal Championship at WrestleMania in a match that has been promoted in advance, and has received all the fanfare of a world championship match on the road to WrestleMania?
I believe the latter is far more likely.