Within the spring of 2018, President Donald J. Trump signed a legislation that watered down the landmark regulatory reform act that his predecessor had enacted following the worldwide monetary disaster. The adjustments received a shocking supporter: the liberal former congressman Barney Frank.

Mr. Frank was a main architect of the Wall Road Reform and Client Safety Act, higher often known as Dodd-Frank. However since his retirement in 2013, he had repeatedly voiced assist for softening one of many legislation’s key planks: that any financial institution with greater than $50 billion in belongings ought to face particularly intensive federal supervision.

The following tweak — lifting the edge to $250 billion — had massive penalties. Amongst different issues, scores of very giant banks would escape, at the very least initially, the Federal Reserve’s annual “stress exams” and revel in simpler financial-safety necessities.

One beneficiary of the change was Signature Financial institution, a New York lender whose board of administrators included Mr. Frank.

Now Signature is useless — a sufferer of a fast-moving disaster that has revealed the extent to which the banking business and different opponents of presidency oversight have chipped away on the strong regulatory protections that have been erected after the 2008 monetary meltdown.

On Sunday, regulators shut down Signature, fearing that sudden mass withdrawals of deposits had left it on harmful footing. Its failure got here barely 48 hours after the collapse of Silicon Valley Financial institution, whose executives had joined Mr. Frank in efficiently pushing to carry the $50 billion threshold.

The back-to-back financial institution failures have unnerved buyers, prospects and regulators, kindling fears of a repeat of the 2008 disaster that toppled lots of of banks, led to huge taxpayer-financed bailouts and despatched the economic system right into a tailspin.

Federal regulators scrambled to defuse the state of affairs, vowing to guard all deposits at Silicon Valley and Signature, and asserting an emergency lending program for different struggling banks. Even so, shares of regional banks have been decimated on Monday, with some falling by greater than half as some prospects rushed to withdraw deposits.

A lot of that regulatory infrastructure stays in place, and the business is by most accounts on a lot sounder monetary footing than it was 15 years in the past.

In an interview on Monday, Mr. Frank, who joined Signature’s board two years after he started calling for adjustments to the legislation, argued that the regulatory rollback didn’t set the stage for the current collapses or a broader banking disaster.

But a number of the banks now dealing with crises of confidence are the identical ones that in recent times have been telling lawmakers and others that they have been sufficiently protected and that they shouldn’t be the main focus of zealous federal supervision.

Lots of these banks argued that onerous federal laws would make it more durable for them to function alternate options to giants like Financial institution of America, JPMorgan Chase and Wells Fargo. But these behemoths at the moment are more likely to see an inflow of deposits as skittish prospects rush for security.

And whereas regional banks managed to persuade lawmakers that they weren’t systemically necessary again in 2018, regulators have apparently concluded in any other case in current days. They agreed to rescue depositors at Signature and Silicon Valley Financial institution for the sake of safeguarding the broader monetary system — a strong reminder of how fears about a few banks, even when they aren’t America’s largest, can shortly infect a whole business.

President Barack Obama signed the Dodd-Frank legislation in July 2010. On the signing ceremony close to the White Home, he effusively thanked Mr. Frank and his co-sponsor, Senator Christopher Dodd, for having labored “day and evening to result in this reform.”

The legislation was a direct response to the brutal disaster that had simply ended. However it was additionally a repudiation of the laissez-faire regulatory method that had develop into ascendant in the US and different nations over the previous a long time. Financial institution executives and lobbyists had persuaded policymakers that years of fats earnings have been proof that they knew tips on how to handle their corporations safely.

With that argument debunked, Dodd-Frank imposed quite a lot of measures to hem within the banking business. There was a ban on sure sorts of dangerous buying and selling. There have been harder necessities to ensure that banks had the capability to soak up sudden losses and to face up to sudden depositor exoduses. And there have been common well being checks to make sure that banks may stand up to worst-case financial eventualities.

From the second the legislation went into impact, the banking business sought to rescind or at the very least calm down it. Its argument was that onerous laws constrained the business’s capability to lend cash to creditworthy prospects.

The argument fell on deaf ears with Mr. Obama within the White Home. Mr. Trump was extra receptive. Barely every week after taking workplace, he referred to as Dodd-Frank “a catastrophe” and instructed reporters that “we’re going to be doing an enormous quantity on” the legislation.

His high officers, a lot of whom had labored in or adjoining to the banking business, started loosening the reins. Generally that meant tweaking guidelines; different instances it meant merely being nicer to regulated banks.

On-the-ground examiners have been urged to be much less confrontational and to supply banks with constructive suggestions, not simply criticisms. Mr. Trump’s comptroller of the forex, one of many high federal monetary regulators, described banks as his company’s “prospects.”

“Altering the tenor of supervision will most likely really be the most important a part of what it’s that I do,” Randal Ok. Quarles, who was accountable for financial institution regulation on the Federal Reserve, mentioned in 2017.

That yr, Republican lawmakers crafted payments to calm down Dodd-Frank. One focus was the supply that subjected any financial institution with greater than $50 billion in belongings to endure stress exams, to take care of better monetary reserves and to give you plans for a way the financial institution may very well be shut down in a disaster.

The laws adopted years of stress from financial institution executives and lobbyists, together with Greg Becker, who till Friday ran Silicon Valley Financial institution.

“With out such adjustments, S.V.B. seemingly might want to divert vital assets from offering financing to job-creating corporations within the innovation economic system,” Mr. Becker warned lawmakers in 2015.

Harris Simmons, the chief government of Zions Bancorporation in Utah, was one other attempting to get out from underneath what he seen as onerous federal supervision. He mentioned that regional banks like his posed little, if any, menace to monetary stability and that powerful laws have been crimping their capability to serve prospects.

“If laws on regional banks have been eased, these banks would have extra capital — as a lot as $4 billion annually — to lend,” Mr. Simmons wrote in American Banker journal in 2017. To bolster his case, he cited Mr. Frank’s assist of elevating the $50 billion threshold.

Zions, which has greater than 100 branches in three states, is now among the many banks being pummeled by anxious buyers. Its shares sank about 25 p.c on Monday. A Zions spokesman didn’t reply to a request for remark.

Supporters of the 2018 adjustments mentioned they nonetheless made sense, whilst a brand new disaster unfolded. “These mid-sized banks wanted some regulatory reduction,” Senator Mark Warren, Democrat of Virginia, mentioned on ABC Information on Sunday.

Within the interview on Monday, Mr. Frank mentioned the laws’s objective had been to concentrate on the nation’s very largest banks and to not saddle smaller establishments with stringent guidelines or oversight.

If the $50 billion threshold had remained in place, Signature would have both wanted to cease increasing or been topic to the Federal Reserve’s stress exams and different necessities designed to curb aggressive risk-taking and guarantee its security.

As a substitute, due to the 2018 change, Signature was free to have a development spurt. It went from about $47 billion in belongings on the time to $110 billion final yr. It expanded into six states.

One current supply of development was cryptocurrencies; beginning in 2018, the financial institution had been among the many few lenders to just accept deposits within the type of crypto belongings. By Friday, issues in regards to the financial institution’s publicity to cryptocurrencies had set off a lethal run on its deposits.

Mr. Frank, who obtained greater than $2.4 million in money and inventory from Signature throughout his seven-plus years on the board, left the job on Sunday as regulators dissolved the board. He mentioned on Monday that the financial institution was the sufferer of overzealous regulators. “We have been those who they shot to encourage others to keep away from crypto,” he mentioned.

He added that despite the fact that Signature had obtained much less federal scrutiny than it in any other case would have, state regulators in New York had nonetheless been on high of the financial institution.

“I didn’t see any diminution of the supervision we have been getting,” Mr. Frank mentioned. “There was quite a lot of scrutiny.”