#3 It's a filler feud for Randy Orton
Of course, Randy Orton beating Bray Wyatt for the WWE Championship at WrestleMania 33 wasn't ideal, but among the benefits was that it would mean a future championship clash between Orton and AJ Styles.
Those two did battle for the first time ever on SmackDown Live in February and produced a barnburner of a bout, leaving fans anxiously awaiting the rematch.
However, you aren't going to do a such a marquee match on a B-level pay-per-view like Backlash, nor should Baron Corbin be rushed into the main event picture. He is more of a long-term project, whereas Mahal likely won't amount to much beyond Backlash.
That isn't to say WWE should give up on pushing Mahal once he presumably falls short of winning the title at the event, but it makes sense for a one-off match at a smaller show. From there, Orton can enter programs with other top-tier talent and Mahal may just go back to being an enhancement talent.