Nearly all established sports are going through some degree of hand-wringing over attracting younger fans as their older core ages out. The death of monoculture and explosion of entertainment options, many accessible without leaving one’s bedroom, have seen attendance drops across the board. MLB and NFL teams have fallen over themselves installing on-site daily fantasy lounges to lure second-screeners. Even the hidebound International Olympic Committee has made transparent plays for youth, most recently with the addition of skateboarding, surfing and three-on-three basketball to next year’s Summer Olympics in Tokyo.

The demographic they’re so thirsty for could be found in droves over the weekend at New York’s Billie Jean King National Tennis Center, where three days of sold-out crowds turned out for the biggest video game competition of all time – the Fortnite World Cup – where a 16-year-old from Pennsylvania named Kyle Giersdorf (aka Bugha) brought home the winner’s share of $3m with a dominant performance in Sunday’s solos competition. It was the climax of a three-day marathon that saw a staggering $30m in prize money doled out.

A walk around the sprawling grounds where the US Open will take place next month raised a pressing question: not whether esports is the future of sports entertainment, but whether there’s any possible scenario where it’s not.

Fortnite, the free-to-play sensation published by Epic Games in 2017, is a crossover phenomenon that raked in $2.4bn in revenue last year alone, transcending gaming into the mainstream in ways few titles have managed. The premise is simple: 100 empty-handed players are dropped onto a virtual island and fight to be the last person standing. Simple to learn, difficult to master.

Quick Guide What is Fortnite? Show What is Fortnite: Battle Royale In short, it's a mass online brawl where 100 players leap out of a flying bus on to a small island and then fight until only one is left. Hidden around are weapons and traps, and players must arm themselves while exploring. When was it released? Fortnite started in July 2017 as a four-player cooperative survival game, but the game's developer, Epic, noticed the huge success of PC title PlayerUnknown's Battlegrounds (PUBG), which pits 100 players against each other, and decided to release a new version. How much does it cost? The game is free and players are able to unlock new items as they progress without paying anything. A Premium Battle Pass gives access to exclusive clothing and items. However there is an in-game currency, V-Bucks, which players can use to buy additional custom gear. It is how this currency is paid for that has become the centre of a dispute between Fortnite's makers and Apple and Google. Why is it so popular with kids? It's free, it's fun, and it has a very silly, offbeat sense of humour. While PUBG has a serious, realistic visual style, Fortnite: Battle Royale has very bright, almost cartoon-like graphics, as well as loads of ridiculous items and costumes, such as space suits and dinosaur outfits. Players can pull a variety of dance moves, and team up with a friend to compete as a duo or a squad. Participants can chat as they play using headsets and microphones. Is there violence? And is it addictive? Although Fortnite is a multiplayer shooter, it does not depict bloody violence. It takes lots of enjoyable gameplay concepts from more mature shooting games but places them in a non-threatening, non-realistic world. In terms of addictiveness, Fortnite contains nothing that makes it different from other action video games. It's more that the game contains many different elements – nice visuals, good shooting mechanics, an interesting building component and lots of support and interest from YouTubers – into one package that is free to download. Photograph: fortnite

About 40 million of Fortnite’s more than 250 million registered players competed in online qualifying over 10 weeks for the opportunity to come to New York. The 200 finalists (average age: 16) hailed from 34 different countries.

The open format meant that some of the game’s most famous players, like Twitch megastar Tyler “Ninja” Blevins, failed to qualify for Sunday’s solo finals. The 28-year-old from Detroit instead settled for a spot in Friday’s pro-am, a nod to the game’s democratic and sometimes random underpinnings.

“It was invite-only before, but I do like that the World Cup is open qualifiers,” said Aydan Conrad, a 20-year-old from Ohio who competes for Ghost Gaming. “Technically, everyone has a chance, and I really like that. I’ve never even met half of the people who qualified here, and it’s cool that they get the chance to come here and make at least $50,000. Some of these kids are 13 or 14, so that’s pretty nice.”

A fan takes in the action on Friday at the Fortnite World Cup. Photograph: Johannes Eisele/AFP/Getty Images

The three-day World Cup finals consisted of a creative competition and pro-am on Friday and the duos competition on Saturday and the singles championship on Sunday. The players manned their stations on a state-of-the art two-storey playing stage with screens depicting each player’s view in the game.

Wall-to-wall color commentary of was broadcast on Fortnite.com, YouTube, Twitch, Facebook, Mixer and Caffeine. Some of the platforms allowed viewers to focus on their preferred player. The telecast featured all the hallmarks of a major sporting event: breathless announcers, splashy graphics, soft-focus profiles of the competitors that wouldn’t feel out of place in NBC’s Olympics coverage.

Stuart Saw, the head of esports at the sports and entertainment company Endeavor who headed the event logistics, said the number of feeds going into the production truck was twice that of the Super Bowl with several dozen in-arena and in-game cameras in addition to the individual displays for each of the 100 players.

The biggest names on the Fortnite circuit are global celebrities, teenage millionaires with social-media followings rivaling the world’s most famous athletes. You may not have heard of 21-year-old Turner “Tfue” Tenney, but your niece probably has. It’s a generational disconnect that even the biggest stars reflect on.

“After high school, my dad didn’t make me get a job right away and decided to give me a year to try and make a career out of this,” Conrad said. “I told him, ‘Dad, if I make what you make in a year, then I get to keep going.’ And then I made that in like, a month. I remember I played the second actual money tournament for Fortnite from home, and my dad was right with me while I was streaming. I ended up making $10,000 and it was a really great moment.”

That esports are big business is hardly news, but the splashy investment figures of the last decade have not always resonated with sports fans older than, say, 25. And yet esports have already been confirmed as a medal sport for the 2022 Asian Games. Addition to the Olympic program would seem inevitable, though some in the industry say the esports doesn’t need the IOC as much as the other way around – and a reluctance to surrender its autonomy, and authenticity, could pose a formidable obstacle.

The communal passion throughout the weekend was palpable. The doors for Sunday’s solos final opened at 9.30am, but fans were lined up as early as 6am for limited-edition special codes redeemable for rare items that could be used in the game. The expansive 46½-acre property of the National Tennis Center allowed Epic Games to transform the venue into an immersive fan festival with DJ booths, carnival-style games and a zipline that saw fans queued up for hours.

The masses filed into the stadium just after midday on Sunday for a concert by DJ Marshmello followed by the hotly anticipated solos final, which consisted of six matches scored on a point-based system that combined placement and number of eliminations to incentivize more active play.

Bugha’s $3m check was not the only life-changing windfall of the day. Psalm earned $1.8m for second, Epikwhale won $1.2m for third and Kreo brought in $1.05m for fourth. The 25th through 100th place finishers took home the princely sum of $50,000 apiece just for showing up, roughly the same as a first-round loser at next month’s US Open.

Fans packed out the home of the US Open for the Fortnite World Cup. Photograph: Johannes Eisele/AFP/Getty Images

Yet a common refrain among many of the players was that money was secondary to the experience – and the life lesson of the pastime that connects them.

“I think there’s something to be said about not just Fortnite, but competitive gaming in general in terms of what it can teach people,” said Sam “Twizz” Pearson, a 23-year-old from New Zealand. “You see that in some of the younger players here not only in the hard work and dedication that they put in, but in their time management. There’s a balance to keep of how much time you spend playing the game, reviewing your game, and working on your skills outside of the game.

“Another thing is communication. It’s very important to have really good communication skills when you want to work with someone and play in duos. These kinds of skills, as well as knowing that you will make mistakes and being accepting of them, will help you take the ego out of your game and analyze things from an outside point of view. Those are the kind of skills that really show in these players and I think that’s what competitive gaming can teach you.”