Marvel has gotten very good at taking advantage of their own success. Over the years, Marvel has made characters popular, sometimes as sidekicks and sometimes in team books, and pushed those characters to the moon. This will usually involve them getting a miniseries, and a character has truly made it when they finally get an ongoing. A solo ongoing is the ultimate test for a character. They're the stars of the show, and they have to be able to keep everyone interested.
Source：https://www.cbr.com/marvel-heroes-no-solo-ongoing-comic/
