i think Wanda absorbed some of Vision's energy/essence/soul when she destroyed the Mind Stone in his head, in Infinity War. she never had time to deal with her grief, ptsd, and his energy adrift in her consciousness, because she got snapped out with everyone into that limbo, which has still never been delved into by the writers. were they dead or some purgatory/parallel limbo?

so Wanda returns, fights in Endgame and almost destroys Thanos in her unresolved rage/grief. after the battle, she crashes hard from all the emotion and turmoil of waking up in 2023, five years of her life gone/missing, her significant other still deceased, and no way to handle it. after fighting to see Vision's lifeless body, she realizes she can't change the actual reality, so she creates her own reality, and resurrects Vision using that energy/essence that she absorbed from him. it is not a complete essence, hence his memory loss before Westview.

the whole series is her living the life she wanted with him, the life she never really got growing up in Sokovia. it's her way of dealing with her grief and ptsd, without going over the edge into the abyss, but it's a fine line. i thought the plots and acting were great, you could really feel the pain of both Wanda and Vision when they have their argument, he wanted answers and she wanted to just exist/feel nothing, no pain. it blew up in both their faces.

i really believe that whatever Shuri downloaded from Vision, in Wakanda in IW, is the missing pieces Vision needs, now that Westview Hex-Vision transferred his energy to real-world White Vision, before Wanda's Westview Hex-Matrix dissolved. the White Vision (canon to the comics) hopefully will eventually become full Vision in the MCU and return to Wanda at some point.

i give WandaVision 9.5 out of 10, great acting and story, movie-quality effects, tight pacing, some interesting time effects and use of colors, love seeing Darcy, Agent Woo, and Monica again..

rest in peace, Maria Rambeau