Then you noticed the cagey wording: "marked as classified". This puts the status of the documents in doubt. Declassification is a process, not an event. The docs go through channels, where the redactors do their stuff. These channels can get very sluggish when under new management. The FBI is one of those channels. A "classified document" in Washington is what the civilian world calls "stationery" or "scrap paper". So sure, Trump broke some laws. Purloining office supplies, at a minimum. Those manila folders with all the supersecret stampings are really cool to have around to show your friends, for those who have friends. Stick a potato salad recipe inside one and you got yourself a state secret. Put in an 8x10 glossy of the Executive Hemorrhoids and you've moved up to Top Secret.
None of the above is important. Trump is just a pawn here. This affair is about the election; a Republican House means the wrong sort of people will be asking awkward questions. The FBI does not want that. The Rs will screw it up, but why take a chance.
What happened here is that Trump and the Archive were tidying up loose ends regarding Presidential memorabilia - routine stuff. The FBI saw an opportunity to gin up a national security crisis and seized it. CNN piled on. The secret nature of the "evidence" gave them a free hand to fabricate any story they liked. Nukes! Iranians! Chinese!
No Russians this time round, though, the editors judged a second term as Russian agent would be a hard sell. Trump is therefore now a freelance foreign agent, selling to all and sundry. It's all bollocks. Any docs Trump took, legally or otherwise, are going to feature Donald J Trump. i.e., this case is about birthday cards and the like.
The sad reality is, Trump will sell anything, but with two important provisos: It must have the Trump brand on it and must not be worth the price asked.
How do I know all this? From everyone's most trusted authority - anonymous sources close to the matter. See how easy that is?