Lindsay Ellis analyzes film trends and history on her YouTube channel. Her latest video, "The Death of the Hollywood Musical," examines the economics of film musicals in the late 1960's.
She cites Hello, Dolly! as the film that temporarily killed the genre. I was surprised at first as she cites plenty of films of lower quality (Dr. Doolittle, Paint Your Wagon, Camelot). She clarifies that it was from a financial standpoint. I was surprised to learn that the studio's had banked hard on Doolittle's success to create a franchise-worth amount of merchandise, most of which went straight to the landfills.
Hollywood executive logic continues to baffle me when it comes to the way some of these films were produced and cast.