Wanda Maximoff has been riding the line between hero and villain for a while. The Infinity Saga has seen the good side of Wanda, making all the sacrifices for a greater cause. However, Doctor Strange in the Multiverse of Madness flipped her to the dark side as Stephen Strange fled from the Scarlet Witch across the multiverse. Since the film's premiere, fans have been at each other's throats about the decision to make Wanda a villain. Some expressed frustration towards her villainy, while others enjoyed Sam Raimi's daring discovery of the Scarlet Witch's potential.
No doubt, making Wanda a villain had a critical upside. It not only made the horror-infused multiverse travel possible but also saw Strange taking the necessary step to play with the Darkhold. In the end, Wanda sacrificed herself in Mount Wundagore's destruction, redeeming her heroic nature -- a moment not unlike Darth Vader's redemption in the Star Wars original trilogy. However, Wanda's previous journey in the character-focused Disney+ series, WandaVision, seemed to have formed different interpretations among fans, which led to Multiverse of Madness' mixed response.
WandaVision imagined a scenario where Wanda was completely lost in her illusions after Vision's death, but the television series was ambiguous enough not to take a stand between good and evil. WandaVision experimented with the extents of Wanda's grief, in which she enslaved an entire town to create her happy ending. With external help, Wanda eventually realized her own doing and set everyone else free.
Multiverse of Madness, on the other hand, took a stand and made her the bad guy, but her villainy had apparent flaws. Wanda was neither an evil being nor was she the real antagonist. Wanda was only a villain because the Darkhold corrupted her. Compared to the threat of a Sinister Strange in the making, the Scarlet Witch was only grieving on her terms. Instead of helping her with grief, the sorcerer became an obstacle in her way, which fueled Wanda's rage and made her killing more ruthless than ever. This particular twist in the storyline also seems to be the reason behind fans' divided reactions.
Raimi has admitted that although Multiverse of Madness is closely connected with WandaVision, he did not finish watching the entire television series. His choice undoubtedly gave him more creative freedom to imagine Wanda's next step in the Marvel Cinematic Universe, but it also created a certain disconnection that would frustrate knowledgeable fans. Wanda has walked a steep path between villainy and heroism. True, she had the potential to be the MCU's worst nightmare, but the Infinity Saga has stabilized the character with the good in her nature.
Wanda Maximoff first made her MCU debut in Avengers: Age of Ultron as a strong opponent to the Avengers. Upon discovering Ultron's plan to destroy the entire world, Wanda turned to the side of the heroes and helped the Avengers to stop Ultron, during which she lost her brother, Pietro. She then joined the Avengers. In Captain America: Civil War, Wanda attacked Vision and took Captain America's side as opposed to Tony Stark's. Later during Infinity War, the character leaned even more heavily toward the heroes' side as they fought Thanos.
It made sense to explore the dark potential in Elizabeth Olsen's character in Phase Four since she certainly did bear the potential that only existed in fans' imaginations. However, due to the previous development in the Infinity Saga, flipping her entirely to the dark side would also be challenging. In fact, flipping any Avenger to the dark side would expose them to a similar risk (consider Chris Evans as a sinister Captain America who decided to take revenge on the government).
The MCU's Wanda Maximoff simply had too much good in her nature to follow the same route as the comics' Wanda. Making Wanda a villain in Doctor Strange in the Multiverse of Madness would attract controversy regardless. Despite the divisive fan reactions toward the Scarlet Witch, her evil outbreak seemed to serve a glorious purpose in the Multiverse of Madness and the MCU.
Doctor Strange in the Multiverse of Madness is available to stream on Disney+.