For many years, just about the only person who thought that companies would want to relocate to the World Trade Center site was Larry Silverstein, the scrappy real-estate developer who had a lot of financial reasons to believe so.

When families pushed to preserve the original 16-acre site as a memorial, Mr. Silverstein, who has the right to rebuild most of the site with office towers, pushed back. When the Mayor started talking about the need for more schools and housing in the area, Mr. Silverstein countered that there was nothing more important than making sure lower Manhattan regained its stature as the world’s financial capital.

Then, lo and behold, it did.

At least a little. Say what you will about Mr. Silverstein—an aide to former Governor Pataki once called him “greedy”—but his worldview won out June 14 when JPMorgan Chase announced it would build a 40-story building on Liberty Street and move 7,000 employees there from midtown. In fact, so much had the world turned over the past year and a half that Mayor Bloomberg, once a downtown skeptic, was singing the financial district’s praises.

“Today you have a booming downtown. You have very little space to build buildings in this city,” he said. “Our problem is an embarrassment of riches.”

Still, Mr. Silverstein’s victory over the doubters may have been largely pyrrhic. It is not he who is receiving the $290 million payout from Chase after all, but the Port Authority, which wrested control over the Deutsche Bank property from Mr. Silverstein in a series of exhausting negotiations last year intended to make sure, among other aims, that at least part of the site could be turned into hotels or apartments.

“It is a little bittersweet for Larry,” said Kent Swig, a like-minded real-estate developer who has bought three million square feet of office space in lower Manhattan since the September 2001 attacks in the belief that the market would come back. “When they went out and took back that property through a negotiation, they were saying, ‘We don’t believe the numbers.’ At the same time, they are living those numbers now.”

Mr. Silverstein, through a spokesman, declined to be interviewed. But minutes after the Chase press conference ended, he sent out a press release to reporters—just in case anyone worried he might be sulking about being left out.

“JPMorgan Chase is a tremendous addition to the new Downtown,” the statement read. “Like the Goldman Sachs headquarters and the speedy lease-up of 7 World Trade Center, it proves again that Downtown has re-emerged as the financial capital of the world.”

It may be a little premature to declare that Mr. Silverstein has been vindicated. He still has 6.2 million square feet to lease in Towers 2, 3 and 4, all scheduled to be finished by 2012, and another 475,000 square feet in 7 World Trade Center, which is already completed. But the Chase deal shows just how quickly fortunes can change in real estate, and how the lengthy production cycle requires developers to be thinking one or two economic cycles ahead.

In March 2006, Class A landlords in the financial district were asking for an average of $42.70 a square foot in rent annually and the vacancy rate reached 11.2 percent, according to Colliers ABR, a real-estate services firm. Deputy Mayor Dan Doctoroff testified to the City Council that month that Mr. Silverstein would not have enough money from rents and insurance payments to see through the complete building of the site, and therefore something had to be done.

He recommended that the Port Authority take over part of the site and change the plans, so that 700,000 square feet of apartments and 700,000 square feet worth of hotels could be built.

“But uses are much less important than is speed,” he said. “It is only important to the extent that the economics of residential are so much more favorable than office.”

Mr. Doctoroff predicted that in order to make office buildings economically feasible, rents “would have to rise to $70 a square foot by 2011.”

That may or may not happen, but in the past year, downtown rents have climbed more than 25 percent, to $53.49 a square foot, according to a Colliers report from May 2007, and the vacancy rate, including space for sublease, is down to 7.4 percent.

The Mayor and then-Governor Pataki succeeded in persuading Mr. Silverstein to give up his rights to develop the Deutsche Bank site and the Freedom Tower in return for low-interest Liberty Bonds and guaranteed government tenants in the towers he still controls.

Mr. Doctoroff did not return requests for an interview by deadline. At the press conference for the Chase tower, he remarked upon the changing fortunes of Ground Zero without mentioning his personal role in it.

“To think back to over a year ago,” he said, “when the memorial was hundreds of millions of dollars over budget and we were fretting that Silverstein wouldn’t have the money, that he didn’t have a resolution to the insurance situation, and today to go to that site and be aware that this is really one of the most important catalysts possible.”

Chalk it up to the waning memories of tragedy, or the lack of alternatives elsewhere in Manhattan. Because of the improved desirability of downtown real estate, the city and the state were able to drive a hard bargain with JPMorgan Chase and limit the subsidies the company will receive—to the extent that $230 million worth of subsidies, which is how much state officials estimate the package will be, qualifies as limited.

“I think this reflects the renewed confidence of the commercial market downtown,” said Robert Yaro, president of the Regional Plan Association.

Mr. Yaro was one of those, from the very early stages, critical of the idea of replacing the roughly 11 million square feet of office space that were in the old World Trade Center with 10 million square feet of office space in the new one. In October 2004, the Civic Alliance, a coalition founded by the R.P.A., put out a report recommending that “housing, hotel/hospitality, and an expanded civic and cultural program” be explored for the World Trade Center site instead of that much office space.

In November 2005, after Mayor Bloomberg began agitating to get rid of Mr. Silverstein, the Civic Alliance joined two other groups in supporting “the Mayor’s recent assertion that the program for the site, 10 million square feet of office space, and the terms of the lease all require reconsideration,” according to a statement at the time.

Mr. Yaro now says, however, that his efforts to create more residential uses on the site had more to do with lightening the area’s density—a battle won, he said, when the Deutsche Bank site was incorporated into the plans.

“We always thought that maintaining the core of Class A office space was important,” he told The Observer. “We just wanted to see a better mix of activities, better retail and cultural activities, and we called for thinking it out.”

But the bank site, now Chase’s future investment-banking headquarters, was slated for some of the 10 million square feet of office development as early as 2002, and formally adopted by all parties in November 2004. Mr. Yaro did not explain why he continued to push for more housing even after that date.

“Everything is a matter of timing,” said Marc Shapses, senior managing director at Studley, a tenant-side real-estate brokerage. “As it turns out, Larry was right on, but I think the writing was on the wall.”

Most observers agree that the Chase deal will help Mr. Silverstein indirectly. “They have added credibility to the site,” said Steve Malanga, a senior fellow at the Manhattan Institute. “There are still several towers down there that have to be rented, but all indications are that major tenants are talking to Silverstein and the Port Authority, and of course the towers themselves do not go up for another couple of years.”

But part of what made the Deutsche Bank property attractive to JPMorgan Chase was exactly that it was not controlled by Mr. Silverstein, but was available for a long-term lease. After all, there are advantages to building and owning: The company gets full control over who else shares the building, which can be attractive to security-conscious banks, and it also gets to write off the asset’s depreciation.

“We don’t want to comment on any particular developer,” said Joseph Evangelisti, a company spokesman, in an e-mail. “But it is fair to say that the 5 W.T.C. site was especially appealing because we were able to build and design a facility ourselves from the ground up for our own use.”

Mr. Silverstein, of course, may have plenty of private tenants to choose from that would like to rent space in Towers 2, 3 and 4, but he has not made any deals so far. Which means that even if he won the bet over the office market, he hasn’t taken home any money yet.