“At some point, it changed when the board was made aware that the rate of donations that were pledged was not near what was received,” Mr. Dunn said. “In addition to that, there was a large donor who had advised the board that the donation was actually an estate gift that was going to be paid when she died, and that she was feeling quite healthy.”

Mr. Dunn said that the overstatement of pledges was a factor in Ms. Sanders’s termination but that there were other management issues as well. “I don’t believe that there was fraud in terms of willful intent,” he said. “I believe that there was information that was misrepresented.”

On Monday, Mr. Weaver, the spokesman for Ms. Sanders, said, “The fact that the pledges did not necessarily come through does not mean they were not valid when made.”

Mr. Weaver also characterized the investigation as politically motivated. He said it had been set in motion by Brady Toensing, a lawyer who filed a complaint about the land deal with the United States Attorney’s Office for the District of Vermont in January 2016 on behalf of various Catholic parishioners. A spokesman for the office did not respond to a telephone message on Monday.

“We request an investigation into what appears to be federal loan fraud involving the sale of the Roman Catholic Diocese of Burlington headquarters,” to Burlington College, Mr. Toensing wrote in a letter to the federal prosecutor’s office.

“This apparent fraud resulted in as much as $2 million in losses to the Diocese and an unknown amount of loss to People’s United Bank, a federally financed financial institution,” the letter said. At the time, Mr. Toensing was the vice chairman for the Vermont Republican Party. He later became the state chairman for Donald J. Trump’s presidential campaign.

The Post reported that the diocese and the college had reached a settlement on the debt.

Mr. Toensing’s letter ended on a political note.

“Ms. Sanders and her husband have built political careers pontificating against corporate corruption and claiming to want to help the needy,” it said. Part of the mission of the diocese was to serve the needy, the letter continued, and the financial loss as a result of the failed real estate deal would “materially detract from this charitable work.”