Well, guess what, Marvel stans? Kevin Feige remember, too, and in a new interview with Rolling Stone he’s got some answers for you!
First off, Doctor Strange was definitely supposed to appear in WandaVision, in the very final episode but Feige balked because “it would have taken away from Wanda, which is what we didn’t want to do. We didn’t want the end of the show to be commoditized to go to the next movie — here’s the white guy, ‘Let me show you how power works.’”
And since that ending would have led even more directly into Doctor Strange in the Multiverse of Madness than the actual, somewhat ambiguous ending of WandaVision already does, they had to make adjustments to that movie too, to account for the fact that the pair hadn’t already discussed her actions in Westview.
But then there’s the matter of those commercials, which were heavy with Wanda-specific symbolism but that we never got any real indication of the nature or greater meaning of. Those were supposed to be Strange himself creating TV-appropriate illusions in an attempt to reach Wanda and shake her out of her fantasy world. Rolling Stone says that WandaVision head writer Jac Schaeffer wanted Cumberbatch to appear as Strange in one of those commercials, but alas, it wasn’t to be.