“Either Doctor Strange simply didn’t view all possible futures, Doctor Strange lied, or a Sacred Timeline in which Loki never stole the Tesseract and the Avengers still ‘won’ was never possible to begin with.”
An Avengers theory about Doctor Strange is doing the rounds.
Doctor Strange needed Tony to live in order for Tony to sacrifice himself and defeat Thanos.
The theory looks back at the moment in Avengers: Infinity War when the Sorcerer Supreme, played by Benedict Cumberbatch, handed the Time Stone over to Thanos (Josh Brolin) in order to save Iron Man’s life.