WandaVision was never cancelled. It was designed as a one season series. That's why the last episode is called "The SERIES Finale" and not "The SEASON Finale".
The marvel shows are meant to be long format movies, not standard TV shows, while some like loki may get second seasons it is more like a movie getting a sequel then actually a second season because it is not a continuation, but rather a follow up
WandaVision was never going to have multiple seasons, it was always intended to be a one-and-done. Besides, with the format the show had, where do you go from there?
There was never any plans to make Wandavision multiple seasons. It was always meant as a limited series as a prelude to Doctor Strange 2. Same thing will happen with Moon Knight, the series will lead to a Midnight Sons project with Blade
