Kevin Feige, the president of Marvel Studios, shared that the character of Doctor Strange has allowed him and the studio to expand the entire MCU as it's one character which is integral to the cinematic universe.
Feige said he wanted to make Doctor Strange primarily because he represented an entire area of the Marvel universe that wasn't explored, "For years we were intrigued with the idea of making a Doctor Strange movie because we thought he was a great character and had a great supporting cast, but primarily because he represented an entire area of the Marvel universe we hadn't explored."