#2 AJ Styles uses underhand tactics to steal a win

AJ Styles is one of the best heels on SmackDown and it wouldn't be out of the realm of possibilities for him to cheat Matt Riddle out of the title. Maybe Styles even distracts Riddle in some way, shape or form, which takes his attention away from the match and ultimately secures Riddle's defeat on SmackDown.
If nothing else, Styles cheating to win on SmackDown could be a turning point in the career of Matt Riddle and put him on the road to title gold. Fans will rally behind Riddle after his loss, while a match at Extreme Rules would be a much better place to crown him as champion as well.
In the end, Matt Riddle might lose a little bit of momentum in defeat, but it would be a lot more fulfilling to see him win the title at Extreme Rules or further down the line. Whether WWE decides to go in this direction or not remains to be seen, but it would make a better story to hold off on crowning Riddle champion.