Lawmakers and regulators have spent years erecting laws and rules meant to limit the power and size of the largest U.S. banks. But those efforts were cast aside in a frantic late-night effort by government officials to contain a banking crisis by seizing and selling First Republic Bank to the country’s biggest bank, JPMorgan Chase.

At about 1 a.m. Monday, hours after the Federal Deposit Insurance Corporation had been expected to announce a buyer for the troubled regional lender, government officials informed JPMorgan executives that they had won the right to take over First Republic and the accounts of its well-heeled customers, most of them in wealthy coastal cities and suburbs.

The F.D.I.C.’s decision appears, for now, to have quelled nearly two months of simmering turmoil in the banking sector that followed the sudden collapse of Silicon Valley Bank and Signature Bank in early March. “This part of the crisis is over,” Jamie Dimon, JPMorgan’s chief executive, told analysts on Monday in a conference call to discuss the acquisition.

For Mr. Dimon, it was a reprise of his role in the 2008 financial crisis when JPMorgan acquired Bear Stearns and Washington Mutual at the behest of federal regulators.

But the resolution of First Republic has also brought to the fore long-running debates about whether some banks have become too big too fail partly because regulators have allowed or even encouraged them to acquire smaller financial institutions, especially during crises.

“Regulators view them as adults and business partners,” said Tyler Gellasch, president of Healthy Markets Association, a Washington-based group that advocates greater transparency in the financial system, referring to big banks like JPMorgan. “They are too big to fail and they are afforded the privilege of being so.”

He added that JPMorgan was likely to make a lot of money from the acquisition. JPMorgan said on Monday that it expected the deal to raise its profits this year by $500 million.

JPMorgan will pay the F.D.I.C. $10.6 billion to acquire First Republic. The government agency expects to cover a loss of about $13 billion on First Republic’s assets.`

Normally a bank cannot acquire another bank if doing so would allow it to control more than 10 percent of the nation’s bank deposits — a threshold JPMorgan had already reached before buying First Republic. But the law includes an exception for the acquisition of a failing bank.

The F.D.I.C. sounded out banks to see if they would be willing to take First Republic’s uninsured deposits and if their primary regulator would allow them to do so, according to two people familiar with the process. On Friday afternoon, the regulator invited the banks into a virtual data room to look at First Republic’s financials, the two people said.

The government agency, which was working with the investment bank Guggenheim Securities, had plenty of time to prepare for the auction. First Republic had been struggling since the failure of Silicon Valley Bank, despite receiving a $30 billion lifeline in March from 11 of the country’s largest banks, an effort led by Mr. Dimon of JPMorgan.

By the afternoon of April 24, it had became increasingly clear that First Republic couldn’t stand on its own. That day, the bank revealed in its quarterly earnings report that it had lost $102 billion in customer deposits in the last weeks of March, or more than half what it had at the end December.

Ahead of the earnings release, First Republic’s lawyers and other advisers told the bank’s senior executives not to answer any questions on the company’s conference call, according to a person briefed on the matter, because of the bank’s dire situation.

The revelations in the report and the executives’ silence spooked investors, who dumped its already beaten-down stock.

When the F.D.I.C. began the process to sell First Republic, several bidders including PNC Financial Services, Fifth Third Bancorp, Citizens Financial Group and JPMorgan expressed an interest. Analysts and executives at those banks began going through First Republic’s data to figure out how much they would be willing to bid and submitted bids by early afternoon Sunday.

Regulators and Guggenheim then returned to the four bidders, asking them for their best and final offers by 7 p.m. E.T. Each bank, including JPMorgan Chase, improved its offer, two of the people said.

Regulators had indicated that they planned to announce a winner by 8 p.m., before markets in Asia opened. PNC executives had spent much of the weekend at the bank’s Pittsburgh headquarters putting together its bid. Executives at Citizens, which is based in Providence, R.I., gathered in offices in Connecticut and Massachusetts.

But 8 p.m. rolled by with no word from the F.D.I.C. Several hours of silence followed.

For the three smaller banks, the deal would have been transformative, giving them a much bigger presence in wealthy places like the San Francisco Bay Area and New York City. PNC, which is the sixth-largest U.S. bank, would have bolstered its position to challenge the nation’s four large commercial lenders — JPMorgan, Bank of America, Citigroup and Wells Fargo.

Ultimately, JPMorgan not only offered more money than others and agreed to buy the vast majority of the bank, two people familiar with the process said. Regulators also were more inclined to accept the bank’s offer because JPMorgan was likely to have an easier time integrating First Republic’s branches into its business and managing the smaller bank’s loans and mortgages either by holding onto them or selling them, the two people said.

As the executives at the smaller banks waited for their phones to ring, the F.D.I.C. and its advisers continued to negotiate with Mr. Dimon and his team, who were seeking assurances that the government would safeguard JPMorgan against losses, according to one of the people.

At around 3 a.m., the F.D.I.C. announced that JPMorgan would acquire First Republic.

An F.D.I.C. spokesman declined to comment on other bidders. In its statement, the agency said, “The resolution of First Republic Bank involved a highly competitive bidding process and resulted in a transaction consistent with the least-cost requirements of the Federal Deposit Insurance Act.”

The announcement was widely praised in the financial industry. Robin Vince, the president and chief executive of Bank of New York Mellon, said in an interview that it felt “like a cloud has been lifted.”

Some financial analysts cautioned that the celebrations might be overdone.

Many banks still have hundreds of billions of dollars in unrealized losses on Treasury bonds and mortgage-backed securities purchased when interest rates were very low. Some of those bond investments are now worth much less because the Federal Reserve has sharply raised rates to bring down inflation.

Christopher Whalen of Whalen Global Advisors said the Fed fueled some of the problems at banks like First Republic with an easy money policy that led them to load up on bonds that are now performing poorly. “This problem will not go away until the Fed drops interest rates,” he said. “Otherwise, we’ll see more banks fail.”

But Mr. Whalen’s view is a minority opinion. The growing consensus is that the failures of Silicon Valley, Signature and now First Republic will not lead to a repeat of the 2008 financial crisis that brought down Bear Stearns, Lehman Brothers and Washington Mutual.

The assets of the three banks that failed this year are greater than of the 25 banks that failed in 2008 after adjusting for inflation. But 465 banks failed in total from 2008 to 2012.

One unresolved issue is how to deal with banks that still have a high percentage of uninsured deposits — money from customers well in excess of the $250,000 federally insured cap on deposits. The F.D.I.C. on Monday recommended that Congress consider expanding its ability to protect deposits.

Many investors and depositors are already assuming that the government will step in to protect all deposits at any failing institution by invoking a systemic risk exception — something they did with Silicon Valley Bank and Signature Bank. But that’s easy to do when it is just a few banks that run into trouble and more difficult if many banks have problems.

Another looming concern is that midsize banks will pull back on lending to preserve capital if they are subject to the kind of bank runs that took place at Silicon Valley Bank and First Republic. Depositors might also move their savings to money market funds, which tend to offer higher returns than savings or checking accounts.

Midsize banks also need to brace for more exacting oversight from the Fed and the F.D.I.C., which criticized themselves in reports released last week about the bank failures in March.

Regional and community banks are the main source of financing for the commercial real estate industry, which encompasses office buildings, apartment complexes and shopping centers. An unwillingness by banks to lend to developers could stymie plans for new construction.

Any pullback in lending could lead to a slowdown in economic growth or a recession.

Some experts said that despite those challenges and concerns about big banks getting bigger, regulators have done an admirable job in restoring stability to the financial system.

“It was an extremely difficult situation, and given how difficult it was, I think it was well done,” said Sheila Bair, who was chair of the F.D.I.C. during the 2008 financial crisis. “It means that big banks becoming bigger when smaller banks begin to fail is inevitable,” she added.

Reporting was contributed by Emily Flitter, Alan Rappeport, Rob Copeland and Jeanna Smialek.