After a year of rumors, offers, final deadlines and final, final deadlines, the owners of Manchester United on Sunday announced that they had sold a minority stake in the team, English soccer’s most successful club, to the British petrochemical billionaire Jim Ratcliffe.

The sale of the 25 percent stake in United, the former English and European champion, was confirmed by representatives of United and INEOS, Mr. Ratcliffe’s company, and announced by the club on social media.

In addition to acquiring a significant ownership stake, Mr. Ratcliffe also agreed to provide another $300 million “intended to enable future investment into Old Trafford,” the club’s iconic stadium. As part of the deal, INEOS was given responsibility for managing the team’s soccer operations, granting it effective control over “all aspects” of the United men’s and women’s teams and also the club’s youth academy.

The deal concluded a chaotic process that many of the team’s fans had hoped would end with something far more significant: the departure from the club of the team’s current owners, the Florida-based Glazer family, which has controlled United since acquiring it in a leveraged buyout in 2005.

Instead, the Glazers will remain the team’s majority owners while netting a sum that values Manchester United around $6.3 billion, or more than five times the amount the Glazers paid to buy it almost two decades ago. And in deputizing the INEOS Sports group — which already has interests in soccer, auto racing, cycling and rugby — to run the soccer operations, the Glazer family may insulate itself from the harshest criticisms of fans.

“Through INEOS Sport, Manchester United will have access to seasoned high-performance professionals, experienced in creating and leading elite teams from both inside and outside the game,” the United co-chairmen and brothers Joel and Avram Glazer said.

Mr. Ratcliffe, through INEOS, agreed to pay $33 per share for his 25 percent stake, a price that represents a nearly 70 percent premium on the current value of the team’s shares on the New York Stock Exchange.

“As a local boy and a lifelong supporter of the club, I am very pleased that we have been able to agree a deal with the Manchester United board that delegates us management responsibility of the football operations of the club,” Mr. Ratcliffe said in United’s statement on the sale. “Whilst the commercial success of the club has ensured there have always been available funds to win trophies at the highest level, this potential has not been fully unlocked in recent times.”

The sale process began more than a year ago, kicked off by an offhand comment from Elon Musk on social media that he was buying the club. Musk later said his offer had been a joke, but the Glazers were apparently serious about hearing more.

United hired the U.S.-based merger and acquisition specialist Raine Group to manage a prospective sale after the firm secured a record price, roughly $3 billion, for another English club, Chelsea. When the Glazers made clear they were open to hearing offers, bidders quickly lined up, including not only Mr. Ratcliffe, but also an American investment fund and a Qatari businessman with links to some of the Gulf country’s most influential figures. Their offers seemed to rise with each new media report.

The entire process took place against a backdrop of months of conflicting headlines, fan protests and swings in the club’s stock price — and all as the team, once a fixture at the top of the Premier League standings, struggled for consistency, and wins, on the field.

“It’s been a process that’s been all about the best interests of the Glazer family above the interests of the club,” said Duncan Drasdo, a United fan and the chief executive of the Manchester United Supporters’ Trust, a group that has protested the club’s ownership since the Glazers first arrived at Old Trafford.

The nature of the original acquisition saw the Glazer family’s late patriarch, Malcolm, burned in effigy, and prompted the Premier League to belatedly draw up regulations so such a transaction could not be repeated. The Glazer family took control after borrowing the majority of the cost of their 805 million pound takeover (roughly $1 billion today) against United’s previously debt-free balance sheet. In the two decades since, the club has paid more than £1 billion in interest and other costs related to the Glazer takeover, while its debt has now surpassed £1 billion, too.

The decision to consider even a partial sale was celebrated by the team’s enormous fan base when it was announced in November 2022. By then United had gone almost a decade without a Premier League title, a championship it last celebrated in 2013, and been usurped as English soccer’s dominant club by its cross town rival Manchester City, thanks to the backing of a member of the ruling family of the United Arab Emirates.

A similar possibility for United emerged when the businessman son of one of Qatar’s men, the former prime minister Hamad bin Jassim bin Jaber Al Thani, announced his intention to buy the team. That offer was widely promoted on social media by fans, influencers and even former players, including Rio Ferdinand, a former captain, who in June created a frenzy and a spike in United’s share price when he announced a sale to the Qatari group was “imminent.”

That proved to be a false dawn. And it was not the only one. Other headlines in British news media, which treated the takeover in ways more typical of high profile player trades in the transfer market, led to similar lifts and dips in both hopes and the price of United shares.

The conclusion of the sale process will not produce the outcome many fans had hoped to see: the Glazers’ sale of the team. Mr. Ratcliffe now will control only 25 percent of the club’s voting rights through a mix of the Glazers’ stake and a portion of those owned by other shareholders. As part of the deal, the Glazers will relinquish day-to-day control of the sporting activities of the club but will retain control of United’s commercial activities and still hold the majority of board positions.

Mr. Ratcliffe seemed pleased with the deal he had made — “We are here for the long term,” he said of his new management team — but the reaction of fans might not be as universally positive.

“I think the problem with it is that it leaves the fan base feeling divided,” Mr. Drasdo said. “It leaves a sense of resentment and negativity that’s not helpful. A clean break would have been better.”

Fans will be hoping the new era will lead to a return of United’s winning ways, and a reversal of the botched succession planning that followed the retirement of the legendary coach Alex Ferguson after he led the team to the last of its 19 league championships in 2013. Since then, new coaches have come and gone, and vast sums have been spent on new recruits. But without a discernible strategy, the club now finds itself with a bloated and underperforming roster, and clinging to eighth place in the 20-team Premier League.

“It’s better than the status quo,” said Andy Green, a board member of MUST and the head of investments at Rockpool, a private equity firm. “Because they have proved themselves as being absolutely appalling at being football club owners.”