WandaVision’s episode 8, titled “Previously On,” explains Thanos’ Soul World scene from Avengers: Infinity War. To obtain the Soul Stone on Vormir, Thanos sacrificed his daughter Gamora, tossing her over a cliff in exchange for the Infinity Stone that brought him one step closer to achieving his nefarious goals for Earth. After snapping half of the world’s population out of existence, the Soul Stone was able to communicate with the Mad Titan, showing him a young version of Gamora while inside the stone. At first, it seemed like a one-off moment meant to showcase what Thanos had lost and the guilt he may have felt due to his actions. However, WandaVision sees something similar happen with Wanda Maximoff and the Mind Stone, suggesting that the Infinity Stones’ abilities are emotionally reactive.
In WandaVision’s penultimate episode, Wanda is forced to take a trip down memory lane by the recently revealed witch Agatha Harkness. She revisited several key moments from her life — watching old American sitcoms with her parents and twin brother Pietro in Sokovia, her parents’ death, becoming a volunteer for HYDRA’s experiments, growing closer to Vision, and the moment in which she brought Vision back and created a sitcom reality out of Westview. However, it’s Wanda’s connection to the Mind Stone (which boosted her already present powers) that allowed her to communicate with Vision inside the alternate world she created.
The Mind Stone was effectively showing the Scarlet Witch the one person she cared for and wanted back the most, seemingly boosted by her incredibly raw emotions of grief at the time. It makes sense because Wanda had just returned from seeing Vision’s body, which was being dismantled by S.W.O.R.D., and being so close to him once more confirmed that she could no longer feel his presence. Thus, the Mind Stone’s powers allowed her to do so again by bringing him back. All told, Wanda’s revival of Vision gave her what she wanted based on her most dominant emotions at the time of his recreation.
This lends credence to the idea that Thanos was able to see Gamora immediately following the snap in Infinity War because he was still feeling grief over her loss despite the fact that he was the one to kill her. With the Mad Titans’ feelings being so potent, the Soul Stone revived young Gamora, perhaps knowing that he longed to see and speak to her one last time after what he did. Their exchange saw her questioning his actions in a brief moment of doubt before he was thrown back into the real world. With that in mind, it’s possible the Infinity Stones only act on heightened and intense emotions, which would also explain why Tony Stark was able to see his daughter in the Soul Stone in a deleted scene from Avengers: Endgame.
Basically, Thanos and Wanda were able to manifest Gamora and Vision through the Soul and Mind Stones because it was their heart’s desire to see the people they cared about the most in a moment of emotional vulnerability. The scene of revival in WandaVision offers further clarity on what happened with Thanos and speaks to the Soul Stones’ enhanced and powerful abilities. Surely, there’s a lot more to discover with regards to the Mind Stone’s abilities, but the fact that it revived Vision the way it did Gamora indicates the strong connection the Infinity Stones cultivate with their users and goes a long way to explain Thanos’ Soul World scene in Infinity War.