Movie Trailers may have started out as a tool to sell films, but over time they have evolved into their own spectacle. Before a film is released there are a multitude of Theatrical Trailers, TV Spots, Web Shorts, and even Trailers before the Trailer starts. How did Hollywood turn from a simple marketing tool, to a an ever expansive industry of movie trailers that mostly give away the entire plot of the film? How did Hollywood crush the Movie Trailer?
“These days”? They always have.
I don’t think it really started until the 1980s? OPs video seems to suggest that.
Take a look at this old trailer, there’s no way you would guess the plot from that.