A theory surrounding Doctor Strange’s involvement in Thor: Ragnarok requires the former neurosurgeon’s knack for healing. In the Marvel comics literature, Thor’s severe injuries in a specific battle leaves him with a broken hammer. Mjolnir needs a fix and only someone with mystical abilities can do that.
And since Stephen Strange has the Eye of Agamotto, another Infinity Stone, he can do so. A theory surrounding Thor’s hammer, Mjolnir,