Only recently it was all over the news that Biden held Senatorial documents he wasn't entitled to take(Google it if you don't believe me), and that he had to give them back. Some of them were held in the secure location of the trunk of his car. Believe me when I say the squabbling over return of documents is something that every administration goes through. Often it's not entirely clear what can be held by a President and what cannot. It's why every former regime has the same issues.
Except every other administration gives them straight back when it is realised that they should not have them. As you are the one screaming "But wHAt abOuT BiDEn?" it's worth noting that it was one of his representatives who found the documents, realised they shouldn't be there, notified the relevant parties and sent them straight back.
What they didn't do is
Have the National Archives ask for the restricted material back
Squabbling for months
Send only send some of them back
Refuse to cooperate meaning a search warrant is needed to retrieve the rest of the material
Mishandling of classified material is bad. It doesn't matter who does it. Just how badly, deliberately, covertly, constructively it is done means it is a bad thing to different degrees.