How did movie trailers evolve into tiny blockbusters?

Internet nerd-dom had an outrage flashpoint recently when trailers for the upcoming movie Terminator: Genisys revealed multiple major plot twists, effectively spoiling what may have been the most interesting (or only interesting?) parts of the movie. Contrast that with the ominous trailer for the first Terminator movie. How did we go from brief teasers to mini-movies that leave out everything but the ending?

Culture website Hopes & Fears put together an excellent, extended article exploring the timeline of  the movie trailer and, drawing on other writing by film critics and experts, figuring out how film trailers became their own industry in miniature. Author Matthew Schimkowi presents a convincing chronology, starting from their origins as advertisements for serials and following all the way up to the advent of the Inception "BWAAAM" noise. Influential individual trailers get mentioned too, including The Public Enemy, Jaws and Dr. Strangelove. By 2015, he argues, the familiar trailer structure for conveying characters and plot arcs has become its own form of entertainment.

This is a highly recommended read for people interested in the film business, but we warn you that it might ruin trailers for you in the future. You'll be the one yelling about "turn lines" the next time you go to the movies.