A young Hollywood producer happened to like a book that no one else really did. When Charles Webb's The Graduate came out, it got lukewarm and mixed reviews. Fortunately for the history of cinema, it struck a chord with producer Lawrence Turman, who decided to option the film rights to the book for $1,000 of his own money (this was in 1964). He felt that the main character had a kind of Holden Caulfield vibe and inhabited the same world of youthful alienation as himself.

So he started to assemble a crew who he thought could do the movie justice. He got Mike Nichols—hot off the success of Who's Afraid of Virginia Woolf?—to direct, and eventually pegged Buck Henry to adapt the screenplay (after an unsuccessful attempt by one Calder Willingham). They were all pretty young and all felt a connection with the main character, Benjamin Braddock (the graduate of the title). Another producer, Joseph Levine, got on board, and later commissioned a college publicity tour that sent Dustin Hoffman to campuses to drum up an audience for the movie.

Turman played an extremely important role in creating the movie. He wasn't the kind of producer who tries to screw things up, only to be resisted by a valiant director, but was himself a creative force behind the film. Adapting it was his idea, after all, and he tapped Nichols to direct and rejecting screenplays from other writers before (correctly) settling with Buck Henry. Plus, he was able to smirk at his naysayers when the movie eventually became a huge success. (Source)

Turman went on to produce other successful movies, though many of them are wildly different from The Graduate, like John Carpenter's horror-sci-fi hit The Thing (1982) and a violent drama about racism and white supremacists, American History X (1998).

Like we said…wildly different.