An hour into “Blood Brothers,” the Netflix documentary detailing the relationship between Muhammad Ali and Malcolm X, we see the young Black heavyweight champion looking perturbed during an interview with a white news reporter.

The interview asks about Malcolm X’s role in Ali’s joining the Nation of Islam, a Black nationalist organization, and Ali, wearing a black jacket, a white shirt, a black bow tie and a hint of a scowl, parries the queries. He concedes that Malcolm, who had recently split with the Nation of Islam, was his “brother,” but wouldn’t call the civil rights leader a friend.

“He was a brother of mine,” Ali said. “Whatever he do, he’s my brother.”

The brief scene exposes the fault lines running under that phase of Ali’s career — his shattered relationship with Malcolm, and Malcolm’s bitter exit from the Nation of Islam, to which Ali remained loyal. It also gives viewers a glimpse at the man behind the boxing myth, someone who showed normal human feelings — like pain over a breakup with a friend and annoyance at a reporter’s questions — not often ascribed to larger-than-life figures.

And it helped capture why, 57 years after he first became heavyweight champion, Ali remains irresistible to filmmakers, and why audiences are especially drawn to him in 2021, when activism by athletes on social issues is often intertwined with their actions on the field.

“Ever since America discovered Muhammad Ali, we’ve been trying to figure out who he really is,” said Johnny Smith, a history professor at Georgia Tech, and co-author of the book “Blood Brothers,” which spawned the Netflix film.

“Blood Brothers” is one of two documentaries, along with “Muhammad Ali,” a PBS film from Ken Burns, his daughter, Sarah, and her husband, David McMahon, to hit screens last month. Last December, Amazon Prime released “One Night in Miami,” a dramatic imagining of a real-life meeting between Ali, Malcolm X, the football star Jim Brown and the soul singer Sam Cooke.

The timing of the projects is a coincidence. Ken Burns said the release dates for the other Ali-based films did not affect the timetable for his project.

But it is not an accident. Ali’s stand against the Vietnam War, which triggered the suspension of his boxing license and a three-year absence from the ring, echoes the stand taken by the pro athletes who marched with protesters last year after the police killing of George Floyd in Minneapolis. The recent intersections of sports and social issues makes Ali, always a popular subject for authors and filmmakers, particularly appealing.

“Especially now, because we’re in the time of activist athletes,” said Louis Moore, a history professor at Grand Valley State University in Michigan. “People want to draw comparisons, so there’s always going to be an opportunity to do an Ali thing.”

A partial list of recent Ali titles could keep a voracious reader busy.

“Blood Brothers,” co-written by Smith and Randy Roberts, was published in 2016, as was “Muhammad Ali: A Memoir,” by talk show host and frequent Ali interviewer Michael Parkinson. In 2017 came Leigh Montville’s “Sting Like a Bee,” which followed the fighter’s dispute withe the U.S. government over his military draft status, and “Ali,” a comprehensive biography by the journalist Jonathan Eig. Stuart Cosgrove’s “Cassius X: The Transformation of Muhammad Ali” appeared last year.

And those are just the books.

In addition to the films released this year, actor Michael B. Jordan is developing an Ali series with Amazon Studios, and a scripted series based on “Blood Brothers” is in development.

For sports fans and Ali aficionados, there’s no shame in failing to keep pace. Even people who make their living at the intersection of boxing and Black history can feel overwhelmed.

“I’m always shocked to see something out there, and I’m always thinking, How do you tell something new?” Moore said. “I’m just going to give it a break, but I do feel compelled. I’ve got to watch the documentaries eventually. I’m pretty caught up on books, but there’s always a new book, too.”

But experts also understand why Ali’s life makes for compelling books and documentaries.

The first half of the fighter’s career featured a series of personal reinventions, from ebullient gold medalist, to trash-talking heavyweight contender, to world champion aligned with a Black nationalist religious sect who refused to fight in the Vietnam War. His membership in the Nation of Islam put him at odds with the civil rights leader Martin Luther King Jr. Opposition to the war in Vietnam later made them allies. Those turning points, Smith says, have helped modern audiences process a fractious time in U.S. history.

“He’s a prism for understanding American history,” Smith said. “Ali is unique as an athlete because he didn’t just reflect American society. He shaped the discourse around race and rebellion and religion and war. That’s why he has this enduring importance.”

Moore traces another reinvention to March 8, 1971, when Joe Frazier knocked Ali down in the last round of their historic title fight. Moore’s research of newspaper archives revealed that most predominantly white daily papers still referred to Ali as Cassius Clay until the Frazier fight, but switched to Ali sometime afterward — satisfied, Moore says, that Ali had been humbled.

From there, Ali’s reputation transformed to make him one of America’s most polarizing public figures, then one of its most adored. That trajectory, Burns says, bears thorough, repeated examination.

“He died the most beloved person on the planet,” Burns said. “None of us are going to have that happen, but I want to know how that happens. That’s an endlessly interesting topic, particularly for someone who was so reviled by so many people for so long.”

Ken and Sarah Burns each acknowledged the challenge in finding fresh ways to tell a story as familiar to viewers as Ali’s is. The film projects released this year each take a distinct approach to a well-worn story. Their project follows Ali’s whole life, while “Blood Brothers” focuses on the early 1960s. “One Night in Miami,” as the title makes clear, happens in a single evening.

“We can always learn something from Muhammad Ali and his story,” Sarah Burns said. “In whatever moment we’re currently in, he speaks to us.”

And Ali’s life will probably yield even more books and movies.

Ali plus a rival — say, Sonny Liston or Ken Norton — can spawn a full-length project. A keen storyteller might also spin a book or film from Ali’s novelty fights with the N.F.L. player Lyle Alzado or the wrestler Antonio Inoki, or from his short-lived side hustle promoting fights in Toronto.

“There’s room for 100 more Muhammad Ali films in the next couple of years,” Ken Burns said.