The Great Depression was dragging on, World War II was appearing on the horizon, and American theaters were showing the second movie about the Grand Old South in less than two years. Gone with the Wind was much more popular than its predecessor, the less iconic antebellum romantic drama Jezebel, but U.S. audiences decidedly loved them both. They each starred the day’s most beloved starlets: Bette Davis in Jezebel, Vivien Leigh in Gone with the Wind. Both are self-destructive heroines with a sharp wit and who are hopelessly in love with proper Southern gentleman; both have national disasters at their center (Jezebel’s yellow fever in New Orleans, and Gone with the Wind’s burning of Atlanta); and both idealized the Old South pre–Civil War. Undeniable box office smashes, the two movies were released in consecutive years. If they sound like the exact same movie, it’s because they practically are.

While Jezebel was released 10 months before Gone with the Wind had even started shooting, their timing in the grand scheme of history was almost identical. MGM had already announced Gone with the Wind and began drumming up massive publicity for it well before the movie’s inevitably postponed release. Hype was swirling, and competitive movie house Warner Brothers wanted a piece. Sothey bought the film rights to an unsuccessful 1933 Broadway play, threw a lot of money at a team, and rushed Jezebel through production in less than six months so they could beat Gone with the Wind to market — which they did, handily. Not at all a coincidence, merely capitalism.

But “twin films” (or “Tobies,” as Vulture once suggested naming them) have become a staple of American blockbusters. Keith Simanton, senior film editor at IMDB, told the BBC in April, “I bet if you went out right now, you could find two, three, or more scripts which are about the same thing and haven’t been made. For example, we went a long stretch without any movies about Dunkirk. Yet in 2017 we had two major features about it: Darkest Hour and Dunkirk.”

There are dozens of twin film pairs throughout cinematic history. Here are a bunch of them: 1985’s Real Genius and Weird Science; 1986’s Top Gun and Iron Eagle; 1995’s Babe and Gordy; 1997’s Dante’s Peak and Volcano; 1998’s Deep Impact and Armageddon; 2003/04’s Finding Nemo and Shark’s Tale; 2005/06’s Capote and Infamous; 2006’s The Prestige and The Illusionist; 2011’s Friends with Benefits and No Strings Attached. There are dozens more of these “coincidences.”

But just like their Civil War predecessors, these films’ twinning existence isn’t a coincidence at all. Simanton told the BBC that the most common reason for these twin films to exist is the exact reason Jezebel and Gone with the Wind were both made: a simple race to market. Imitation — or, more vulgarly, plagiarism — is seen as a form of flattery in Hollywood. One studio hears that another is making a movie, presumes it will be fairly popular, and rushes a thematically similar one through production, hoping to beat them to the theaters and steal a bit of the shine. But what makes something an idea worth stealing isn’t just the story—it’s the story’s place in the culture at that exact time.

Sometimes that’s simply an anniversary (like Steve Jobs’ death leading to both Jobs and Steve Jobs in 2013 and 2015, respectively), but often there’s more to it. And that’s what makes the duality of Gone with the Wind and Jezebel so interesting. Both are films about the antebellum South and the Civil War, which arrived in a marketplace that had never before rewarded those kinds of stories. Every Civil War movie before these two bombed at the box office. Before production of the two films, Irving Thalberg, a beloved movie producer, brushed off Gone with the Wind — now known to be one of the most profitable films in American history — saying, “No Civil War film ever made a nickel.” He was right: Until then, that was true.

So why did Gone with the Wind gross approximately $198 million domestically at the time (about $1.8 billion when adjusted for inflation)? And why did Jezebel, which is far less popular today, have absolutely no problem out-earning its incredibly expensive production costs? Because they were both released at exactly the right time. The American world (to be clear, the white, rich, movie-going American world) and culture found itself on a similar precipice as our heroines in these movies. Fear of war resonated for Americans just as it did the heroines of these films. This was a country almost a decade into the Great Depression that would have clearly responded to O’Hara’s Gone with the Wind cry: “I’m going to live through this, and when it’s all over, I’ll never be hungry again—no, nor any of my folks!—if I have to lie, steal, cheat, or kill! As God is my witness, I’ll never be hungry again.”

Audiences also strongly identified with the rebellion of these movies’ heroines. The audience was hell-bent on its own independence, filled with women who had held up the country during World War I and were only a few years out from commanding factories during World War II.

Although about an America decades in the past, these stories were almost tailor-made for the mid-1930s. Just like every twin film after them, they were mirrors held up to the societies that welcomed them, popular even in duplicate for a reason. It isn’t a coincidence that popular culture often welcomes multiples of the same initial idea, but — just like every other coincidence — their existence is only a product of the ideas and lived history that came before them.