The difficulty comes when a sequel moves forward simply because the studio wants it, even before there’s a solid idea to ground the movie in.
The sequel to Edge of Tomorrow came about because the creative people behind the first one wanted to make a sequel for the fans, the idea for the movie came before the green light from the studio.
The movie was successful because lots of people went to see it, and that means there’s an audience that, one assumes, would be interested in a sequel.
Movie studios see a movie that’s successful and they, of course, want to see more of that success.