While Wanda is exercising his grief, it’s possible that he’s busy trying to fix all kinds of issues the cropped up in the magic world while half of life in existence was missing (maybe we’ll even get a taste of what he was up to in the upcoming Doctor Strange In The Multiverse Of Madness).
This revelation admittedly does in part make you wonder why Doctor Strange didn’t have the same kind of reaction to Wanda’s explosive demonstration of power, but it’s also not terribly hard to come up with a No-Prize explanation.
After all, everything that happens in WandaVision takes place only about a month after the events of Avengers: Endgame, and one can imagine that the former brain surgeon was a touch busy during that period – especially given the fact that he was one of the characters who was “blipped” and missed the last five years on Earth.