MOPEDS emblazoned with Manchester United’s crest drone through the streets of Bangkok. Fans in Okene, Nigeria, dance in red and white kits on the town’s annual Arsenal Day. Official supporters’ groups exist in Macedonia, Mongolia and Mexico, some of the 180-plus countries to which matches are broadcast. In the 25 years since it was first contested, the English Premier League, which kicked off a new season last month, has become the most lucrative product in the world’s most popular sport. Its clubs earned £4.5bn ($5.8bn) in the 2015-16 season, almost twice as much as any other football league, according to Deloitte, a consultancy.

The puzzle is that the game’s most renowned domestic competition is not very good. ClubElo.com, which rates teams according to the opponents they beat, calculates that eight years ago four of the world’s five top sides were English. Today none is. An English club last reached the final of the Champions League, Europe’s most prestigious knockout competition, in 2012. A Premier League star last made the top five in the Ballon d’Or, an award for the world’s best player, in 2011. Spain, Germany, Italy and France, the other members of Europe’s “big five”, now dominate. England’s lower-ranked teams are worse than their equivalents in Spain and Germany, too. Yet as the standard of English football has dived, it has only become richer (see chart). Why are such a mediocre bunch so popular?

Two bits of good luck and one dreadful tragedy laid the groundwork. The English language is no guarantee of success (France has the wealthiest rugby competition, for instance) but it makes the chatter between managers, pundits and players more accessible than in Germany or Italy, say. And being in a European time-zone means that early risers in the Americas and night owls in Asia can tune in to matches—something that England makes easier with its afternoon kickoffs, which are handier for Asian fans than Spain’s evening fixtures. The Hillsborough tragedy of 1989, in which a crush killed 96 Liverpool supporters, led to the removal of standing sections in stadiums around the country. Over the next decade clubs spent £500m on renovations, which meant higher ticket prices and richer fans—the “prawn sandwich” brigade, in the words of Roy Keane, a Manchester United captain. At the same time, money flooded into the league from a television deal with BSkyB, a satellite broadcaster, which more than trebled the fee that the previous broadcaster, ITV, had paid.

The biggest change, however, has been in the Premier League’s openness to foreign managers, players and owners. When Arsène Wenger became Arsenal’s manager in 1996 he was only the fourth appointee from outside Britain and Ireland in English history. Today he is one of 13, making the Premier League the only big-five division with a majority of foreigners in the dugout. And whereas on its first weekend in 1992 only 13 of those players who appeared were foreign, last season 69% of squad members were, 12 percentage points more than any other European league.

The expanding circus of international stars has broadened the league’s appeal. South Koreans tune in to watch Tottenham Hotspur’s Heung-Min Son; Senegalese to follow Liverpool’s Sadio Mané. Such players have been acquired partly thanks to injections of foreign capital. Led by Roman Abramovich, a Russian magnate who bought Chelsea in 2003, the Premier League has become a playground for foreign tycoons. They now have controlling stakes in 12 clubs, including smaller ones such as West Bromwich Albion and Swansea City.

English teams have also been quicker than others to market themselves abroad. Manchester United began making regular pre-season trips to Asia in 1995, whereas Real Madrid did so only in 2003. This summer English teams entertained crowds everywhere from Houston to Hong Kong. And they are expanding with business ventures in new corners of the globe. Manchester City owns clubs in New York, Melbourne, Yokohama and Montevideo. With its three African sponsors, Arsenal has as many as continental Europe’s five richest teams put together.

The Premier League has some features which have the effect of lowering its standard but making it more exciting to watch. Its teams bargain collectively for television deals and share the booty more equally than other leagues, which has made for a more competitive division. Real Madrid, Juventus and Bayern Munich take a greater share of their leagues’ profits—indeed, each Spanish team negotiated its own television deal until 2015—allowing them to maintain their boringly dominant positions. In 2016, while the German, French and Italian leagues endured a fourth consecutive year with the same champion, lowly Leicester lifted the title in England—the fourth club in as many years to do so.

And whereas continental teams sensibly pour resources into developing talented youngsters, English teams splurge on ageing stars, who draw in crowds but do less to win matches, according to the 21st Club, a football consultancy. Six of the Real Madrid side that won this year’s Champions League final joined as teenagers. By contrast in recent years a number of English sides have spent club-record sums on older players who are at the peak of their fame but have ended up spending half their time on the bench. Manchester United’s signing of Ángel Di María, a £59.7m flop, is one recent example. The constant hiring and firing of title-winning managers in England similarly makes for great drama, though bad results.

Can this export success story survive Brexit? The pound’s slide has made it more expensive for English clubs to sign and pay foreign players. But given that much of clubs’ earnings are denominated in foreign currencies, sterling’s weakness is manageable. The bigger worry concerns migration. After Brexit, Europeans may face the same immigration rules as everyone else. Star players will have no trouble clearing these hurdles, but lesser-known talent may be excluded. N’Golo Kanté, a young Frenchman who helped Leicester win their league title, had never played for his country and thus would have struggled to get permission to work in Britain had it not been for the EU’s free-movement rules.

There is another problem. Although English clubs have the money to acquire foreign stars, the inability to win big titles is off-putting. Stars such as Robert Lewandowski know that they are more or less guaranteed to win some silverware when they sign for Bayern Munich. A move to Manchester is less likely to lead to glory, even if the wages are as good. This calculation has already lost the Premier League some of its best players, such as Luis Suárez and Gareth Bale.

If it cannot attract football’s megastars, that will limit the Premier League’s appeal to fans. For the time being, clever marketing and a competitive, dramatic league have been enough to keep the world glued to England’s competition. But if they want to keep selling football, English clubs will have to get better at playing it, too.