Days before President Trump was inaugurated, the Consumer Financial Protection Bureau sued Capital One, accusing it of using deceptive tactics that the bureau said cheated customers out of $2 billion in interest payments on their savings accounts.

On Thursday, the bureau abandoned that lawsuit and permanently waived its legal right to ever again pursue the claim.

Russell Vought, the director of the White House budget office, has moved swiftly to close the consumer bureau’s offices and decimate the agency since he took control this month as its acting director. The bureau’s staff has been on administrative leave for weeks, barred from engaging in virtually any work, including representing the bureau in dozens of ongoing legal actions.

Mark Paoletta, brought in by Mr. Vought as the agency’s chief legal officer, quickly ended several of those cases. On Thursday, the agency also dropped litigation against the Pennsylvania Higher Education Assistance Agency for student loan servicing failures; against Rocket Homes Real Estate for what the bureau called a kickbacks scheme; against Heights Finance for cycling struggling borrowers into successive loans that repeatedly incur refinancing fees; and against Vanderbilt Mortgage and Finance, owned by Berkshire Hathaway, for making mortgage loans to consumers who it knew could not afford to repay them.

Last week, the bureau abandoned a case against SoLo Funds, an online lender, for camouflaging fees on its loans, costing consumers more than $20 million. Days later, Mr. Vought called the company “innovative” in a social media post.

“More to come,” he wrote. “The weaponization of ‘consumer protection’ must end.”

Representatives of the consumer bureau did not respond to requests for comment on Thursday about the dropped lawsuits.

“We welcome the C.F.P.B.’s decision to dismiss this action, which we strongly disputed,” a spokeswoman for Capital One said in a statement.

The agency’s case against Capital One accused it of essentially pulling a bait-and-switch, attracting customers with ads for its high-yield savings account, 360 Performance Savings, but steering many of them toward a nearly identically named product, 360 Savings, that paid as little as 0.30 percent annually, even as the Federal Reserve raised interest rates above 5 percent.

The dismissals came as Jonathan McKernan, a former board member of the Federal Deposit Insurance Corporation who is Mr. Trump’s nominee to run the consumer bureau, was testifying at his confirmation hearing before the Senate Banking Committee. Senator Tina Smith of Minnesota, a Democrat, asked Mr. McKernan about the dropped lawsuits.

“This makes me question who is really going to be in charge of the C.F.P.B. if this is what’s happening while your nomination is being considered,” she said.

“If I’m confirmed, I am the director,” Mr. McKernan responded.

“It’s not clear to me, because at the moment that we’re sitting here talking about you taking on this responsibility, Russell Vought or others are dismissing lawsuits that you just told me you were going to have the opportunity to review before they were dismissed,” Senator Smith countered.

Congress created the consumer bureau in 2011 to monitor consumer loans and install safeguards to prevent a recurrence of the conditions that led to the housing crisis. The bureau cannot be shuttered without congressional action, but Mr. Vought has halted nearly all its work. He canceled the agency’s lease on its Washington headquarters; fired nearly 200 of its 1,700 workers and telegraphed plans to lay off nearly all of the remainder; and canceled scores of contracts with outside vendors that are essential to the agency’s daily operations.

Asked multiple times at his confirmation hearing if the consumer bureau should exist, Mr. McKernan repeatedly deflected. “That is a question for our elected officials,” he said.