The Oscar best documentary feature nominee “O.J.: Made in America” is a staggering achievement, a film magisterial in its scope, riveting in its detail. It lets you feel like you’ve finally taken the full haunting measure of the O.J. Simpson saga — cultural, biographical, sociological, legal, forensic. Yet it still seems fair to ask: Why has Ezra Edelman’s five-part epic swept the year-end film critics’ awards, and why is it now the frontrunner to win the Oscar for best documentary? The movie, which is seven hours and 47 minutes long, was first presented as part of ESPN’s “30 for 30” series, (and it now has the distinction of being the longest film ever nominated for an Academy Award). It was conceived, and made, to be shown on television.

That may sound like a quibble. “O.J.: Made in America” has been racking up film honors, and is now in the thick of the Academy Awards race, because it eminently qualifies: It was shown in a handful of movie theaters (beginning last fall), so technically speaking it’s as much of a “movie” as any documentary made this year.

For a while, though, I was a little bothered by how it was shoehorned into the “movie” category. Many acclaimed documentaries — like “Amanda Knox” and “13th” — enjoy relatively brief runs in theaters so they can qualify for Oscars, but they are still aesthetically engineered to be movie experiences. “O.J.: Made in America” was exhibited in theaters so that it could qualify, which begs the question: Does anyone want to see an eight-hour movie in a theatrical setting? There are precedents, of course, like Claude Lanzmann’s nearly nine-hour Holocaust documentary, “Shoah” (1985), which was conceived to be a theatrical experience. But you could argue that “O.J.: Made in America,” by entering the documentary awards race, created an unfair playing field because it seemed to be operating according to different (that is, small-screen) rules.

Most documentary filmmakers have to judge the length of their movies assiduously. To take just one example: The sublime Nina Simone documentary “What Happened, Miss Simone?” (2015) is only 100 minutes long — but with a subject that rich, the filmmaker, Liz Garbus, could easily have made it 150 minutes. She didn’t because that would have been a commercial non-starter. Purists may snipe, but in the real world there are limits to the form of what a movie can be. Later this year, we’ll see Ken Burns’ 10-episode, 18-hour documentary series “The Vietnam War” (scheduled to be shown on PBS in September). Will it be treated as a “movie” if PBS decides to exhibit it for one week in a theatrical setting? I revere Burns’ work, but I hope the answer is no.

Nevertheless, I’ve gotten over my purist attitude toward “O.J.: Made in America.” That’s because I think it could end up having a jolting effect on the documentaries that get made. ESPN set the template, but it is just one of a number of networks that have the potential to back ambitious, paradigm-busting documentary epics. Not every subject is as singular and vast as the O.J. Simpson saga, of course. But one can begin to think of examples — say, a multi-hour panorama of Donald Trump’s rise to power (I can imagine Charles Ferguson, the incisive director of “No End in Sight” and “Inside Job,” making that one), or the culturally wide-ranging, never-before-fully told inside story of Michael Jackson’s life and death (how about Fenton Bailey and Randy Barbato?). With the potential promise of Academy Awards consideration, documentaries like those, designed to be addictively watchable and exploratory landmarks, could be an enthralling addition to the landscape. Like “O.J.: Made in America,” they could become major cultural events.

The upshot is that it doesn’t matter all that much whether documentaries like these end up being experienced on the small or big screen. Let’s be honest: They’re destined to be home-viewing experiences (today, “Hoop Dreams” would probably be a three-part HBO film). What matters is that in an increasingly audacious era for nonfiction, documentary filmmakers like Edelman may now feel, more than ever, like broadening the canvas, busting the boundaries of the forms they’ve been working in, redefining what it looks like when reality becomes the ultimate drama.