I have no idea if Trump thought about declassifying the documents as he sent them to Mar-a-Lago. I do know that if he claims he did, it will be a up to the jury to decide if he did. Judge Cannon will have to instruct the jury - based on case law - that he had the power to do so, and it is up to the jury to decide whether they believe that he is lying. Matter of law, matter of fact.
And if he makes the claim, which I really hope he does, that will open the door for the prosecution to impeach such a claim, see post #298 as an affirmative defense.
And the biggest impeachment is his own action which confirmed he DIDN'T declassify the documents because he still referred to them on audio tape as classified and he accepted the classified nature of the documents as a result of the Federal Court subpoena. He never challenged the subpoena on the basis that he'd declassified the documents and therefore there were no documents to surrender. And his lawyers know how they prosecution will challenge the claim and I'm sure they want to do all they can not to make it in court.
So yes please, make the claim in court.
WW