To anyone that doesn’t know, the investigation he’s referencing was done by a trump appointed Republican special counsel
The report concluded that what trump and Biden did was much different, and that trumps actions were worse by repeatedly lying and stalling and obstructing the process
He declined to press charges on Biden because he felt the jury would feel it was a mistake by Biden and not intentionally done, whereas the case was opposite with trump, who is on tape showing classified documents to reporters and guests and bragging that the documents are not declassified even though they should be
Also, the classified documents trump had pertained to nuclear weapon information, and is so sensitive that it is not able to be declassified by the president alone, but involves a specific process with congress involved