It doesn't seem suspect because once the government found out about the docs they asked for them back. Trump played musical chairs with the documents and hid them not just from the government but from his own lawyers to avoid giving them back. Then he got himself on tape saying basically "Look at this classified document that I'm not keeping secure in any way. When I was President I could have declassified this document just because I wanted to (even though this document shouldn't be declassified) but I'm not President anymore so I can't do that. Yet here it is, I'm waiving it in your face." His housekeeping staff had full access to our classified documents, along with any random guest at Mar-A-Logo. I mean I watched enough 80s spy movies to know that this would be a treasure trove for a secret agent just sitting there asking to be photographed and sent back to the motherland.
In short, Trump has been way way stupider than any of those other Presidents. There is evidence for days. Not just speculation or assumptions. Evidence, the kind you can put in front of a jury in a court room. That's on Trump for being as dumb as he is.