The letter was posted by a conservative journalist.
The journalist pointed to the involvement of the president.
The amount of classified information Trump took with him was shown.
The letter to Trump was published by an ally of the former president.
John Solomon highlighted a letter that showed the involvement of President Joe Biden in the investigation that led to the raid at Trump's home.
The document showed the scale of secret information contained in documents there and how damaging it was to national security.
Solomon's publication of the letter backfired as legal experts said this was the more serious revelation.
The May 10 letter was from a senior official at the National Archives. Solomon was a liaison to the National Archives.
It was addressed from the National Archives to Trump's attorney and discussed the 15 boxes of materials Trump handed over in January, which it said contained 700 pages of classified material.
"In its initial review of materials within those boxes, NARA identified items marked as classified national security information, up to the level of Top Secret and including sensitive compartmented information and special access program materials," Wall wrote.
Three of the highest levels of classification are listed here. It led to an internal assessment of the potential damage caused by the way in which these materials were stored and transported.
US officials have said that getting the documents back was a key reason.
The FBI may not have been allowed to view the documents since Trump's legal team said they were covered by executive privilege.
She wanted to ask Biden if the FBI could access the files, and he delegated that to her. The FBI was able to read them, according to the letter.
Solomon presented the information as proof that "Biden White House was involved" at the beginning of the investigation, but he didn't mention the details of the classified information.
The publication of the letter backfired according to Bradley P. Moss.
Is it possible that the letter is bad for Trump?
The records at Mar-a-Lago were classified, as well as the records at the Special Access program. Our most sensitive secrets are those. The people were sitting in a basement.
The release was both a self-inflicted wound and further proof of how the government has been playing by the rules.
A separate trove of documents to those recovered in the August 8 raid on Mar-a-Lago, which stayed in Trump's hands months longer and included highly classified material, is the subject of a letter.
Business Insider has an article on it.