Chiefs Finally Win One. Brady and Belichick Appear Primed for a Rematch.

MIAMI GARDENS, Fla. — For the first time in what felt like forever, America was treated to a Super Bowl without the New England Patriots on Sunday. The upstart San Francisco 49ers, with their smothering defense, took on the Kansas City Chiefs and their wunderkind quarterback Patrick Mahomes. With aging stars like Aaron Rodgers and Drew Brees also watching the game at home, the Super Bowl looked like a debutante party for the N.F.L.’s next generation.

Yet through it all, the Patriots, who last missed this big stage in the 2015 season, loomed over Hard Rock Stadium like a blimp commanded by the usual villains, Tom Brady and Coach Bill Belichick. The leaders of the N.F.L.’s most enduring dynasty, which seemed to be on death’s door three weeks ago when the Patriots slinked out of the playoffs, all but taunted N.F.L. fans with their mere presence, as if grabbing for the torch being passed.

Brady and Belichick were both on the field before the game, when the top 100 players in N.F.L. history were introduced to honor the league’s centennial season. Brady was shown palling around with his boyhood idol, Joe Montana, as well as with other great quarterbacks, such as Brett Favre, John Elway and Dan Marino. Brady, of course, is the only one still playing.

Then the cameras panned to Belichick, and the boos rained down on the coach who is third on the N.F.L.’s career wins list. Belichick let out a hearty laugh, lifted his hands to the camera and showed off three of his six Super Bowl rings. Point made: I’m great and I’ll be coming for more.

After kickoff, Brady wasn’t done, making the point in, what else, a multimillion-dollar television commercial. In an ad for the streaming service Hulu, Brady mocked the concern about his future, which he had stoked last week with a cryptic post to his social media accounts. Hulu leaned into the worries.

“They say all good things must come to an end,” Brady said in Sunday’s ad while walking into Gillette Stadium, the home of the Patriots. “So it’s time to say goodbye to TV as we know it.”

Cue anxiety.

“But me? I’m not going anywhere.”

Brady can become a free agent next month for the first time in his long career. Patriots fans may fear the worst, with Brady reportedly garnering interest from the Raiders and Chargers. But one thing appears certain: Nobody should be surprised if Brady is playing football next season.

Brady had crashed the Super Bowl before. Ahead of Super Bowl 50, in February 2016, a game between the Denver Broncos and the Carolina Panthers, he was introduced with other Super Bowl greats. The Patriots made it to the Super Bowl the next three seasons.

One of the keys to that run was one of Brady’s favorite receivers, tight end Rob Gronkowski. Gronkowski retired last year, but he made a splash last week partying with fans in South Beach. On Sunday, he was shown yucking it up with Brady and other Patriots elected to the N.F.L.’s team of the top 100 players in its history.

Not going anywhere means Brady will be back giving fits to the Chiefs, 49ers and every other team next season.

Still, Brady, perhaps the best-known player of his generation, is hardly the face of the league anymore. Peyton Manning and Favre appeared in more national ad campaigns during their playing days, and their aw-shucks demeanor endeared them to fans across the country. Brady and his celebrity wife are more secluded from view.

There was daylight Sunday for a breakthrough.

Right on cue, Mahomes, last year’s most valuable player and one of the league’s biggest stars, overcame a rough start in his Super Bowl debut to engineer a stunning fourth-quarter comeback to lead the Chiefs to their first Super Bowl title in a half-century. San Francisco 49ers quarterback Jimmy Garoppolo, once Brady’s understudy in New England, faltered down the stretch. Chiefs 31, 49ers 20. Season over. New era underway. Maybe.

After the game, Chiefs defensive end Frank Clark declared the Patriots dynasty dead.

Mahomes is the new face of the league. At 24, he is the second-youngest quarterback to win a Super Bowl. He has appeared in national advertisements for Head & Shoulders and State Farm insurance. He had the top-selling jersey this season.

Last week, Chiefs tight end Travis Kelce was asked if winning the Super Bowl would make Mahomes the new face of the N.F.L. “I think he already is, if you ask me,” he said.

“He’s got a long shelf life, barring serious injury, and he’s on a team that could be a contender for a long time,” Bob Dorfman, a marketing executive from San Francisco who tracks athlete endorsements, said of Mahomes.

Brady and Belichick, of course, know all about being contenders for a long time. And don’t bet against them coming back and contending again next year.

Benjamin Hoffman contributed reporting.