In spite of right-wing spin, those classified and top-secret documents that Donald J. Trump had stolen and sequestered at his Mar-a Lago roach motel were illegally in his possession. He thinks that retroactively "declassifying" them makes his theft legal. It does not.
This former TV reality show host falsely believes that presidential records are his personal property to do with as he pleases. According to Trump, "It's not theirs, it's mine." Wrong again.
Once Trump left office, all records (classified and declassified), should have been returned to the National Archives. They were not. After claiming that he had not withheld documents from the FBI and DOJ, he sought "executive privilege" over those documents which he had just denied having (FYI, executive privilege does not apply to former presidents).