#4 Having Finn Balor interfere
Let's be honest here.
Finn Balor was nothing more than a prop on Monday Night Raw this past week and only appeared to help Roman Reigns defeat Baron Corbin. Of course, it worked and Reigns was able to dispose of Corbin after a back and forth contest, but fans went wild when Balor came out to make the save.
With that being said, the win, coupled with how he won it and Balor interference, mixed together to create a situation where fans would have to root for Reigns. In fact, even Balor was rubbing elbows with Reigns to help him gain credibility with fans, which really seemed to work and make Reigns come across as even more of a badass.
In the end, it might not be the best use of Finn Balor, but having him come to Reigns's aid is a huge deal and indicative of WWE using other stars to help Reigns get over with the crowd. Furthermore, it seems to be working out quite well, which is another sign that WWE will do this again in the very near future.