Just FYI, none of the statutes cited in the Mar-a-lago search warrant mention 'classification' as a condition.
They are about: Gathering, transmitting or losing defense information, Concealment, removal, or mutilation generally and Destruction, alteration, or falsification of records in Federal investigations and bankruptcy .
Fun fact about classified nuclear information: it can not be unilaterally declassified by the President. Thanks to the Atomic Energy Act, the Department of Energy has to review it, first.
If Trump took nuclear docs to share with, ex, the Saudis, he would certainly have needed help inside the WH to find the docs that would be of interest to them. Because, Trump himself certainly doesn't know the technology, so he wouldn't know which info the Saudis would want. And he probably wouldn't know where to find such documents in the first place. He would have needed a technical expert with some knowledge of how the government stores classified info in order to get the good stuff. Taking everything would be an option, but that's probably hundreds of boxes of stuff.
But still, that first "If" is important.
Here's the most generous take I can come up with:
One of the myths in Republicanism is that Obama ran off to Chicago with millions upon millions of documents. And it's true, he did! He absolutely did. That probably made Trump think he could and should do the same, and that the National Archives and DOJ were just being partisan when they told him to give the documents back.
What Trump is missing, because the Republican myth ignores this, is that all of those Obama documents were cleared by the National Archive, to go to the Obama Presidential library, where they are still maintained by the National Archive. And that's standard procedure. Trump didn't get the documents cleared, and he has no Presidential library. He just grabbed a bunch of documents and took off. And he thinks that fine because he doesn't live in reality; he lives in the Republican mythology, where the tales say Democrats get away with everything, so he should feel free to be just as lawless.
Updated:
A President can't actually unilaterally declassify nuclear secrets anyway. They always have to go through DoE, first.