None of that explains why they didn't put a Black Widow movie on the schedule as soon as the character became a breakout star in Iron Man 2 and The Avengers. Or why they took a risk on both Guardians of the Galaxy and Ant-Man before taking a risk on something that didn't have a white male lead. Besides, look at how many characters Marvel has successfully introduced as supporting players in other movies -- Fury, Widow, Hawkeye, War Machine, Falcon, arguably Coulson, and now both Black Panther and Spider-Man. If they were worried about taking a risk on an unknown character, they could've seeded T'Challa or Carol or whoever in a movie several years ago in order to set up their solo film. So the facts show that they are willing to take a risk on a new male lead character, but have been slow to feature even a popular female character that audiences were already clamoring to see in a solo movie. So if there's any fear of "risk" shaping their decisions, it seems to have more to do with the perceived risk of a non-white or non-male lead than with the risk of an untried premise.