Agents of Shield has always shown some connection the Marvel Cinematic Universe(MCU) movies when they are released while the show is running. When Dr. Strange was released in November 2016, Agents of Shield continued that path as the season went on they have really got into exploring other dimensions, the Darkhold, and creating portals. The way things are going it is inevitable that they run into Dr. Strange at some point. If Dr. Strange has taken the role as the Sorcerer Supreme in the MCU. There is no way he will allow the Darkhold to be in just anybody possession. Dr. Stange duty is to protect the world from mystical threats right?