Right now, Marvel Cinematic Universe is doggedly jumping through every loop and loophole it can to make the next phase of its cinematic universe bigger and better. With Disney+ shows adding another dimension (lol!) to the mix in addition to the comic book source material, things -- as dark Dr. Strange says in the trailer but not in the movie -- just got out of hand.
In his cinematic debut, Strange is more or less the same character -- changes were made to make him fit in line with the impending Infinity War. We're introduced to the character at the height of his arrogance as he pokes fun at public health care, sorts through a drawer full of high-end watches to fit his tux for a speaking engagement, and handpicks his next surgery case.