Whether he sold them or not is irrelevant to the case that's being made so far. He had confidential/classified/top secret documents he shouldn't have had, as a citizen. When the feds learned of this and set up a January meeting to retrieve the documents, he didn't provide the documents requested. When the feds requested he lock up the documents in a safe area, he put them in a storage room where random people could walk in/out.
Yes if he sold them that's treason and he's going to jail forever, but the current case is focused on him having highly classified documents he's not authorized to have, and (allegedly) obstructing the retrieval of them to the point the FBI had no choice but to take them away. I think Trump is a POS sociopath but I wouldn't assume he did something as treasonous as that without charges or accusations being filed about it.
He has no executive privilege as a private citizen. That power rests solely with Biden. If the documents he had were declassified there will be an obvious process trail that proves it. It sounds like some of the documents relate to the Russia-gate thing. Maybe he withheld documents he thought were damning to him. Maybe he withheld documents to reveal his innocence. Who knows. But given that some of the documents, whether they involved Russia-gate or not, included highly sensitive shit like human intelligence agent names...the "declassification" argument further falls apart. He can't wave his hand and reveal the names of spies in foreign countries.
