Denis Villeneuve's Dune adaptation omits information that would've made its first major twist much more shocking. Frank Herbert's science-fiction classic was published in 1965. Dune has seen multiple adaptations since then, including Villeneuve's most recent blockbuster. However, one change in Villeneuve's version arguably lessened the impact of a major twist in the narrative.
Dune 2021 tells the story of young Paul Atreides, who is thrust into war after his family is entrusted with the care of planet Arrakis, causing conflict between House Atreides and House Harkonnen, led by the powerful Baron Harkonnen. The Baron is able to take back control of Arrakis using the terrifying Sardaukar army, but only after doctor Wellington Yueh betrays the Atreides and disables Arrakeen's shields. It is later revealed that Yueh betrayed House Atreides in order to save his wife, who was being held captive by the Harkonnens.
While Villeneuve's adaptation remains faithful to the source material, for the most part, Yueh's storyline is cut down. It's important to note that, in the book, Wellington Yueh is a Suk doctor, which means that he has received Imperial conditioning and is thus unable to betray his masters. This explains why the Atreides and their Mentat, Thufir Hawat, are never suspicious of Yueh. Jessica is convinced of Yueh's hatred of Dune's villainous House Harkonnen, having heard that they had slain the doctor's Bene Gesserit wife, Wanna. This is why it comes as such a shock in the book when Yueh is revealed to be the traitor. This essential backstory is lacking in Dune 2021, however, and so the character of Wellington Yueh seems somewhat less interesting.
This information also contributes to Dune's worldbuilding. Alongside Mentats and the Bene Gesserit, the concept of Imperial conditioning serves to hammer home the fact that psychological manipulation is an important aspect of this universe. Added to this is the fact that the Harkonnen's Mentat, Piter De Vries, was able to bypass the conditioning by finding the right "lever," as he puts it, also characterizes the Harkonnen as a formidable force. Yueh's betrayal of House Atreides despite his conditioning reveals the depth of his love for Wanna, which only makes his fate all the more tragic when he realizes that his wife was dead all along.
It makes sense, then, that Denis Villeneuve originally shot a scene in which Lady Jessica and Dr. Yueh discuss his wife. In this scene, the topic of Yueh's wife was reportedly raised in an emotional manner and featured Wellington Yueh breaking down. Lacking the important background information regarding Yueh's Imperial conditioning, this scene most likely could have served to develop him a little, adding an emotional dimension to the character. Unfortunately, this scene between Jessica and Dr. Yueh was cut from the final version. With a novel as full of details as Dune, it's understandable why certain elements or storylines must be cut out for a movie adaptation, but it's undeniable that the information about Dr. Yueh's backstory would have made his betrayal much more shocking.
