Glass' Clover Twist Has No Set-Up
The second twist in Glass comes later, as the authorities finally swarm the scene of the fight. After Casey Cooke (Anya Taylor-Joy) is able to calm The Beast and let Kevin's personality reassert control, he is shot in the stomach by a police sniper. As David is recovering from having been tossed into a water tank, he has his face forced into a puddle and is drowned by a SWAT officer. Both police officers, along with Dr. Staple, are revealed to have the same tattoo of a three-leaf clover on their wrist.
Before David dies, Dr. Staple allows him to touch her hand, triggering his power to see what evil things a person has done. He experiences a vision of Dr. Staple at a clandestine meeting of several people. We don't learn much about this "Clover Group" beyond the fact that they have been secretly hiding the existence of superhumans for ten-thousand years. She also speaks to Mr. Glass as he is dying, telling him to take comfort in the fact that he was right about people with powers existing, though the comic books had it wrong when it came to the secret societies - her group goes after both heroes and villains to maintain the balance and protect the status quo.
This revelation comes completely out of left field and breaks the pattern of Shyamalan's earlier movies. In the past, whenever Shyamalan employed a twist ending, he would leave the viewer a chance to piece together the mystery before the big reveal, such as in The Sixth Sense, when none of the characters interacting with Malcom Crowe apart from Cole Sear is a hint that Malcolm is a ghost but doesn't realize it. There's barely any indication anywhere that a secret society like the Clover Group exists in Glass before it is revealed during the climax.
The goals of this group and the limits of their power are also ill-defined and illogical. It seems that Dr. Staple is trying to enact alternatives to killing superhumans whenever possible, either by convincing them they are just imagining their powers or developing treatments to keep them from accessing their abilities. Yet the group doesn't hesitate in killing Kevin W. Crumb and David Dunn, who were successfully pacified until Mr. Glass acted. The idea of trying to persuade people they imagined their superpowers doesn't scan either, as Dr. Staple's scientific explanation for David's evil-detecting touch is that he has a talent for cold-reading people like Sherlock Holmes. Ignoring how this was blatantly contradicted by multiple events in Unbreakable, being that good at deduction is a superpower unto itself, as Mr. Glass himself seems to prove.
The Clover Group also seems incredibly blasé about the witnesses of their actions, allowing Joseph, Casey, and Mrs. Price (Charlayne Woodard) to go free after killing their loved ones, apparently confident that no one will believe them if they try to talk to the press. Yet as powerful as the Clover Group apparently is, they weren't able to capture David for the 19 years he protected Philadelphia as The Overseer, despite there being countless videos, photos, and fan pages promoting his existence online.
Glass' Big Twist Makes No Real World Sense
The third and final twist in Glass comes after Dr. Staple has met with her fellow Clover Group members in Philadelphia and assured them that the situation with The Overseer, The Horde, and Mr. Glass has been contained. While visiting a comic book shop, Dr. Staple overhears two fans discussing one villain's scheme and enthusiastically declaring that criminal masterminds never let you know their real intentions and that they employ misdirection like a master stage magician. This leads Dr. Staple to the discovery that Mr. Glass hacked the hospital security system before he and The Beast made their escape attempt and arranged for all the camera feeds to be live-streamed to a secret server.
Glass' final scene takes place in the 30th Street Station in Philadelphia, as Mrs. Price, Casey, and Joseph meet and wait. We find that all three of them were e-mailed the footage of the fight between The Beast and The Overseer, showcasing how both men really did have superpowers, and agreed to post the footage online in the hopes that it would go viral. Glass concludes as audiences see people all around the terminal looking at their phones and their tablets in astonishment, as Mr. Glass' actions reveal the existence of superpowered people to the world and prove that he was right all along.
Ignoring how Mr. Glass' final actions are a rebuttal to the Clover Group, he should have had no idea existed, there is no way this ending works within the context of the world of Glass. We already know from earlier in the movie that The Overseer had a considerable online presence, with hundreds of eye-witness accounts over two decades of David displaying superhuman strength and invulnerability. Given that, a new series of viral videos are not going to sway the cynical public and magically convince everyone that superpowers are real in the "fake news" era, even if the Clover Group doesn't have the ability to keep the videos off of the major national news networks. In the end, this twist breaks the story of Glass as if it were made of the same substance.