On hindsight, the big reveal at the end of Scream Queens revealing Hester to be the brains of the operation, was a obvious. The identities of the killers in “Scream Queens” haven’t really mattered since about the third episode, when it became clear that the show was mostly interested in milking caricatures and seeing how many pop-culture references it could cram into every hour. Fans of the TV show have long had Hester as prime suspect, because that character was completely crazy. But now it should have been more obvious. Because of her casting. Lea Michaels was the star of Ryan Murphy's previous TV show Glee, so casting her in a less important role on Scream Queens was the biggest clue that her role was more than just a bystander.
While the Bathtub Babies and Pete had a clear motive — destroying Kappa and Greek life because of what happened to their mother — the crimes don't make any sense now. Why kill Shondell, the Pizza Guy, and Coney the new mascot? How does that exact revenge? Why kill the Kappa pledges? As outcasts, wouldn't they be the ones to make Kappa a better place? And why kill Chanel No. 2, but none of the other Chanels?
If vengeance were really the motive, why didn't they go after Dean Munsch? She was the one person still alive and on-campus the night their mother died in the bathtub. Why let her live? That doesn't make any sense either. How could they feel any real satisfaction when the one person literally responsible for the cover-up is still alive? Dean Munsch can still be a scourge to feminism everywhere, especially now that she still knows Hester is the killer. Also, wouldn't Hester be mad that Pete killed Boone? Wouldn't she have gone after him?
For me, the real surprise was that Pete was in on the killings. He seemed so honest and committed to finding the truth behind the devils. That was awesome writing.