#1 Turning Braun Strowman heel
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By far the most obvious land most infuriating move that WWE made in order to get fans behind Roman Reigns was how they turned Braun Strowman heel over the course of one night. Not only was that a bad idea since Strowman is the hottest face right now besides Rollins, but also by what it does to Strowman's future.
In fact, WWE could end up just using Strowman to put over The Shield and finally establishing Roman Reigns as the top guy of the company. In the end, if Strowman loses to Reigns for the title, fans are going to lose faith in him and be forced to throw their support behind someone else.
Maybe Strowman will come out on top eventually and give him the run he deserved more a year now, but that seems really unlikely with current booking The Shield right now. Furthermore, it seems very unlikely that WWE is going to waste a title reign on Strowman when Reigns is growing more and more in fan support by the day.