Paul Bettany has told the story several times. When he got the call to do
WandaVision from
Marvel, he originally thought he was being fired. His Marvel contract had run its course after the last
Avengers movies, and when he was called for a meeting with Feige and the Marvel executives — especially after Vision died in
Infinity War and didn’t return in
Endgame — he assumed they were thanking him for work for ten years and saying don’t call us, we’ll call you.
Instead, they were pitching him the idea for
WandaVision.
[...]
If Bettany was worried he was done playing the Vision
before, he sure doesn’t sound so now. Speaking with
Esquire, he was asked if he was going to play Vision “forever,” to which he responded, “I love Vision. Yes, I'm in.”