#2. The crowd turning on Seth Rollins and the heel turn
After Roman Reigns was diagnosed with leukemia and went on a hiatus, it was clear that Seth Rollins would replace him in that top spot in 2019, with his coronation happening at WrestleMania 35. Nobody would have anticipated that he would beat Brock Lesnar in two and a half minutes in the WrestleMania opener.
While he had momentum as the Universal Champion, he would lose the title twice and by late September, the WWE Universe began to sour on him. It became clear at this point that the top babyface role in the company is one that's hard to maintain in modern WWE and it wasn't Roman Reigns' fault when he was in Rollins' position.
Unfavorable comments and more made Rollins a hated babyface and before you knew it, the crowd was clamoring for The Fiend to beat him for the Universal Championship. They got what they wished for and in December, Rollins would turn heel and align with AoP.
It was bizarre because he went from the top babyface spot to the top heel spot within 8 months. At least this time around, WWE listened to the fans.