For a while this weekend, it looked as if Sam Altman might return as a conquering hero to OpenAI, the company whose board had fired him as chief executive on Friday.

It would have been another shocking twist in a saga that was already full of them. And Mr. Altman had a lot of leverage. OpenAI employees had rallied behind him since his firing, and OpenAI’s investors were pushing the board to bring him back. Billions of dollars — and, possibly, the trajectory of the entire A.I. industry — hung on the fate of the board’s decision, and many expected it to cave under pressure and reverse itself.

Instead, the board held firm, rejecting Mr. Altman’s return and affirming in a late-night memo to employees on Sunday that removing him was “necessary to preserve the board’s ability to execute its responsibilities and advance the mission of this organization.” It appointed Emmett Shear, the former Twitch boss, as interim chief.

Hours later, Satya Nadella, the chief executive of Microsoft, announced that Mr. Altman and his top lieutenant, Greg Brockman, would join the tech giant to lead a new A.I. research division.

The OpenAI saga is far from over. Things are shifting quickly, and there is plenty we still don’t know — including the reason the board decided to fire Mr. Altman in the first place. (In the memo on Sunday, the board said there had been no specific incident that led to the firing, but rather that Mr. Altman had simply lost its trust.)

But even without knowing much about the inciting incident, we can start to assess the damage.

Loser: OpenAI

The most obvious loser in all this is OpenAI itself.

Before Friday, the company was the hottest name in tech, with a celebrity leader, a household-name product in ChatGPT, and a murderers’ row of A.I. talent that was the envy of Silicon Valley giants. It was in the middle of a tender offer that would have allowed employees to cash out their stock at an eye-watering valuation, and its cutting-edge A.I. language model, GPT-4, was best in class.

Now, the company is in chaos. Its top leaders are gone. Morale is shattered. The tender offer may fall apart. The new chief executive has said he wants to slow A.I. down. And the company is still highly dependent on Microsoft, which has the enormous computing power OpenAI needs to run its models — and which, as of Monday, will have a mini-OpenAI growing inside of it, led by Mr. Altman and staffed by former OpenAI employees.

OpenAI’s board may be satisfied with this outcome — after all, the board chose it, even after being given a chance to backtrack. But it looks silly for not explaining why it fired Mr. Altman, and until it shares more information, it’s hard to imagine the rank-and-file falling in line.

Winner: Microsoft

No one’s weekend had a bigger turnaround than Mr. Nadella.

On Friday, when Mr. Altman was fired, it looked as if Mr. Nadella might lose one of his most powerful allies. Microsoft invested $13 billion in OpenAI, and under Mr. Altman’s leadership, the company had become a key partner of Microsoft’s. Its technology is the backbone of many of the A.I. services, such as the company’s suite of Copilot A.I. products, that Microsoft is betting the future of its business on.

Mr. Nadella would have clearly preferred to see Mr. Altman reinstated. But when it was clear that wasn’t happening, he did the next best thing: swooping in to offer jobs to Mr. Altman, Mr. Brockman and their loyalists.

Strategically, it was a masterstroke. Now, Microsoft will be able to continue using OpenAI’s models to power its products in the short term, while also giving a new, Altman-led team the money and computing power it needs to build new Microsoft-owned models over the long term. He’ll get a bunch of talented A.I. researchers from OpenAI, and Microsoft now effectively owns 100 percent of a new A.I. lab that any Silicon Valley venture capitalist would have lined up to fund.

Winners: A.I. Doomers and Effective Altruists

For years, a community of A.I. researchers and activists — many affiliated with the effective altruism movement, whose adherents think that reason and data can be used to determine how to do the most good — have warned that A.I. systems were becoming too powerful, and that out-of-control A.I. could pose an existential threat to humanity.

People with these fears — sometimes mocked as “doomers” or “decels” by their critics — were once considered fringe. But over the past several years, they’ve been moving toward the mainstream, gathering signatures on open letters and warning regulators to take A.I. safety seriously. And on Friday, they took down the chief executive of the world’s leading A.I. company.

Ilya Sutskever, OpenAI’s chief scientist, who led the coup against Mr. Altman, is not an Effective Altruist, but he appears to have been motivated by similar fears. And two of the board members who supported the coup, Tasha McCauley and Helen Toner, have ties to Effective Altruist groups.

If OpenAI ends up being irreparably harmed by Mr. Altman’s firing, people will blame the board for breaking one of Silicon Valley’s most promising young start-ups, and destroying billions of dollars in shareholder value.

But the board has clearly succeeded on its own terms. It was worried that Mr. Altman was moving too fast to build powerful, potentially harmful A.I. systems, and it stopped him. That’s a victory for the cause, even if it comes at the expense of the company.

Losers: Investors

No one was rooting harder for Mr. Altman’s return to OpenAI than the investors and venture capitalists who backed him, and who stood to lose their money if he left.

Many of these investors are techno-optimists who believe that A.I. will be an unalloyed good for society, and they loved Mr. Altman’s essentially optimistic take on A.I.’s future. (They also loved that he made them a lot of money.)

These investors now have stakes in a company with an interim chief executive, a work force in revolt and an unclear path forward. What’s worse, the only way they can invest in Mr. Altman’s new company is by buying Microsoft shares.

Unclear: OpenAI’s rivals

It’s not clear yet whether rival A.I. companies will benefit from Mr. Altman’s ouster.

On one hand, companies like Google, Anthropic and Meta could benefit from a weakened OpenAI if it allows them to catch up to the company’s A.I. progress, or siphon off key employees. (Recruiters wasted no time trying to poach unhappy OpenAI workers on Friday.)

But it also means they will be competing with a stronger Microsoft. And it means that Mr. Altman’s new A.I. efforts will not be constrained by the same convoluted nonprofit governance structure as OpenAI was, meaning he might be able to move even faster.