LOS ANGELES — When Jason Kilar began his tenure as the chief executive of Hulu in July 2007, some competitors considered the streaming service so likely to fail that they nicknamed it Clown Co. Yet Mr. Kilar, armed with both the conviction that there was a better way to watch television and the backing of two powerful corporate parents — NBCUniversal and News Corp — sequestered himself and his team in an empty Santa Monica office and got to work. He covered all the windows with newspapers, emphasizing the point that naysayers were to be ignored.

“Sometimes in life, blocking out that outside noise is a really good thing to do,” he said in a recent interview.

Hulu did not fail, and 13 years later Mr. Kilar (the first syllable rhymes with “sky”) is the chief executive of WarnerMedia. Suddenly, he has a lot of noise he needs to ignore.

This month, Warner Bros. announced that its 17 films scheduled for 2021 — including big-budget offerings like “Dune” and “The Matrix 4” — would be released simultaneously in theaters and on the company’s struggling streaming service, HBO Max. The move, orchestrated to deal with the continuing challenges brought on by the pandemic, upended decades of precedent for the way the movie industry does business and sent Hollywood into a frenzy.

Powerful talent agents and theater executives publicly blasted it. Perhaps most important, some high-profile filmmakers who have worked with Warner Bros. — and whom the studio is counting on working with again — were sharply critical. Christopher Nolan, whose “Tenet” is just the latest of his movies released by Warner, told The Hollywood Reporter, “Some of our industry’s biggest filmmakers and most important movie stars went to bed the night before thinking they were working for the greatest movie studio and woke up to find out they were working for the worst streaming service.”

Denis Villeneuve, the director of “Dune,” wrote in Variety that “Warner Bros. might just have killed the ‘Dune’ franchise.” (“Dune” covers only half of the novel by Frank Herbert. The plan was for Mr. Villeneuve to complete the sci-fi tale in a sequel.) Neither Mr. Nolan nor Mr. Villeneuve, nor most of Hollywood, had been told of Warner’s plans before they were announced.

Mr. Kilar, 49, called the pointed criticisms “painful,” adding, “We clearly have more work to do as we navigate this pandemic and the future alongside them.” But he has spent his career pushing against entrenched systems and was somewhat prepared for the outrage.

“There is no situation where everyone is going to stand up and applaud,” he said. “That’s not the way innovation plays out. This is not easy, nor is it intended to be easy. When you are trying something new, you have to expect and be ready for some people who are not comfortable with change. That’s OK.”

Mr. Kilar’s boss, John Stankey, the chief executive of Warner’s parent company, AT&T, also defended the strategy, calling it a “win-win-win” at a recent investor conference.

Earnest and approachable, Mr. Kilar, who took over WarnerMedia in May, comes across more as an eager do-gooder than a ruthless disrupter. Both the childhood stories he tells about rushing home from school in Pennsylvania to watch “Speed Racer” and the enthusiasm he shows for upcoming projects — he called the adaptation of Lin-Manuel Miranda’s musical “In the Heights” “life affirming” — seem aimed at deflecting the growing narrative that he is the evil villain at the center of a plot to dismantle the very act of going to a theater to watch a movie. (In email exchanges after the interview, he shared a list of movies he had paid to watch in theaters before the pandemic shut things down, writing, “Movie theaters are where I have had some of my most transcendent experiences.”)

Mr. Kilar has positioned WarnerMedia’s decision to release films in theaters and on streaming as a reaction to the struggles caused by the pandemic, which has shut down the majority of American theaters and prompted most studios to delay releases into next year. (One notable exception to the delay is Warner’s “Wonder Woman 1984,” which will be released in theaters and on HBO Max on Christmas Day.) He has also called the decision an accommodation for audiences, who have become more accustomed to watching films in their living rooms.

But Mr. Kilar joined WarnerMedia just two months before the lackluster debut of HBO Max, and it is his job to make the service successful.

There are serious challenges. HBO Max is more expensive than other streamers ($15 a month) and has been criticized for lacking any “must see” content. (The mini-series “The Flight Attendant” has recently created some buzz.) Its marketing has confused customers trying to determine the difference between it and platforms like HBO Go and HBO Now. The subscriber total stands at 12.6 million, far behind Netflix (195 million worldwide subscribers) and Disney+ (87 million). Only 30 percent of HBO subscribers have signed up.

On top of that, AT&T’s balance sheet features close to $170 billion in debt, prompting some in Hollywood to wonder if the company can invest enough in content to make its objectives a reality.

So it’s helpful that beneath that “Ah, shucks, I’m just a kid from Pittsburgh” veneer is a relentlessly ambitious executive who in 2011 wrote, on a Hulu blog, a widely read manifesto that criticized the television business — and that most likely played a significant role in landing him his current job. In his short time, Mr. Kilar has restructured WarnerMedia, laid off about 1,000 employees and begun ridding the company of decades-old fiefs.

Some employees appreciate his clear direction and focused approach, while others chafe at what they see is a lack of respect for Hollywood tradition. He has become known for sending long emails, often late at night or on weekends, explaining his thinking.

“If you were going to design an executive for this day and age on paper, Jason Kilar is the ideal person for the job,” Jeff Shell, the chief executive of NBCUniversal, said in an interview. The two got to know each other this past year while hashing out a deal over the “Harry Potter” series of films that Warner produced and Universal licensed for its various channels.

“While it’s well known that he knows tech,” Mr. Shell added, “I do think he has both a respect for content and a relentless desire to pursue where the consumer is going. It was refreshing to see him do such a bold thing.”

Mr. Kilar had never run an organization the size of WarnerMedia, nor did he deal directly with talent and other artists in his past work experience.

For instance, when asked before Mr. Nolan’s public criticism how he thought the filmmaker, a fierce defender of the theatrical experience, might react to Warner’s move, Mr. Kilar was positive.

“I think he would say that this is a company so thoroughly dedicated to the storyteller and the fan that they will stop at nothing to make sure they are going as far as possible to help both the storyteller and fan,” Mr. Kilar said.

Whoops.

Mr. Kilar does admit that the company should have been more sensitive to how its announcement would be received by actors and filmmakers. “A very important point to make — something I should have made a central part of our original communication — is we are thoughtfully approaching the economics of this situation with a guiding principle of generosity,” he said. That blind spot when dealing with creative talent may point to Mr. Kilar’s emphasis on serving the audience above all else. When making the announcement about “Wonder Woman 1984,” he wrote a memo that used the word “fan” or “fans” 13 times. His most recent one, announcing the 17-picture deal, was titled “Some Big 2021 News for Fans.”

Mr. Kilar says that this commitment to the customer took hold during a childhood trip to Disney World. As his story goes, Mr. Kilar, the fourth of six children, was wowed by the company’s attention to detail, from the pristine landscaping to the lack of chewing gum on the sidewalk.

“It moved me in ways I had not been moved before,” he said.

From there, Mr. Kilar became an expert on all things Walt Disney. He read the biographies, scoured the libraries for more material and finally landed an internship at the company after drawing a comic strip when his letters generated no response. He was most interested in Mr. Disney’s entrepreneurial spirit, a quality Mr. Kilar defines as “the relentless pursuit of better ways.”

He sees a direct line from that childhood obsession to his decision as the chief of WarnerMedia to elevate streaming to the level of a theatrical release.

The broader movie industry is not as romantic about it. Mr. Kilar’s primary mistake, as the town sees it, is not the deal itself — after all, filmmakers have been making deals with Netflix for years — but rather the nerve to ignore the other stakeholders when making the company’s decision. He is still viewed as an outsider, one who is discussing revolution but, perhaps, really just trying to prop up a faltering streaming product that needs to gain subscribers quickly to earn Wall Street’s approval.

“There are some things that you can talk and talk and talk about, but it doesn’t necessarily change the outcome,” Mr. Kilar said. “I don’t think this would have been possible if we had taken months and months with conversations with every constituent. At a certain point you do need to lead. And lead with the customer top of mind and make decisions on their behalf.”