it always felt weird that strange went from a total novice in 2016 to casually fighting a 4 stone thanos in 2018.
until you realize the dormammu time loop wasn't just him dying. it was basically an infinite hyperbolic time chamber.
strange didn't just annoy dormammu, he spent decades or centuries trapped in that loop doing nothing but practicing magic against a god. he fights thanos like a 1000 year old sorcerer supreme because mentally, he is one.