I guess it comes down to the same question as “why would he keep any at all?”
It’s a power flex that had no logical motive beyond feeding his own ego and sense of entitlement. “I’ve got a library of top secret documents from my time in the White House” made him feel like a Big Important Person. He is such a fundamentally broken, tiny man.
You’re kidding. Trump doesn’t read. This is clearly used as toilet paper.
You think he uses toilet paper?
Or maybe Saltine Nauta.
From what I understand, many of these kinds of documents aren’t even supposed to be printed, ever, anywhere. They reside on secure, air gapped computers to be viewed only on tablets that are likewise airgapped and must remain within the specific, secure room. No other electronic devices are allowed in the room.
Apparently, presidents are allowed to order them printed (not sure why) but it seems like any such use would be tracked in detail.
First thought I had was the that he hoped to sell some of them.
Second was that he gets a stupid macho kick out of showing them to other boys men.
Trump apparently has a strong distain for computers, so much so that he would have tweets printed out for him.
I dunno a few images are coming together in my mind. For one, his big thing was that he was going to come up with proof of all the shit: Biden, Clinton, Epstein, the big conspiracy. That was his brand and he had four years to look through everything he could. Not personally I’m sure, but I imagine there was an effort to find anything, everything, or at least something that will capture some press. Then, in addition, no doubt he meant to sell some information or trade it for personal favors. Most likely he did so repeatedly.
So I can see him hoarding it for a sense of power and demanding that trusted underlings comb through it and find him something useful.
…The fact that this may have taken the shape in the form of some one rifling through boxes of printed state secrets while sitting on the gilded lid of Trump’s toilet just ads… vibrancy… to what’s already a dysfunctional and chaotic scene.
And yet.
And yet.
My guess is he had enablers, helpers who did printing and boxing and such.
Here’s one scenario:
TFG really was going to and in fact has been selling state secrets but he’s got this big backlog of as-yet unsold product, waiting to connect the right buyers. Since he’s surrounding himself with OnLy ThE bEsT pEoPLe the project has gotten bogged (heh! get it? bog? ) down as his enablers and fellow grifters-in-training have had to work to identify buyers.
Meanwhile, any operative with half a brain books a few days or weeks at Mar-el-Lardo and just takes pictures of everything.
sTeP 3: pRoFiT!1!!11!
ETA:
And @TornPaperNapkin - I should’ve clarified, I meant the only legitimate reason I could think of for any former POTUS or VP to bring a bunch of documents home when leaving office, because we know they all do.
Like, how anyone involved in the packaging and transport of this stuff could’ve thought it was normal, you know?
I expect there’s more to it, but honestly I could see Trump taking boxes of classified documents just so Biden wouldn’t get them. (Yes, I know that’s not how printouts work. It doesn’t change things.)
gotcha. I’m just in awe because normally my worst case scenarios are worse than reality, but this time… damn.
I can imagine, on the one hand, that anyone/everyone who knew better had gotten the hell out (or been thrown out) of Dodge (if they even bothered to show up to work for 45 in the first place), while on the other hand it’s impossible that (even among those willing to have hung on to the end) absolutely no one knew better.
Occam’s Razor leads us to conclude that Trump kept them simply because he believes they are his.
Some pundits are speculating that his egotism is so pervasive that he views everything in his possession as his personal property and that he is loath to relinquish control regardless of legality.
Really he’s nothing but a giant toddler. No further explanation needed.
(and @ClutchLinkey) Because he took them, because he believes that he doesn’t have to abide by the laws of this country. I think that’s the only actual reason why he did this - because he could and he wanted to. 
But I do think he could also want to sell them, because money…
From what I understand, the National Archives works with every President (but not with the VP, which is why both Biden and Pence had papers in their homes) at the end of the term to sort through the mass of papers and where they should go (to the archive and which archive (a future presidential, or some other part of the national facility outside DC, or if they’re “personal” and can be taken out of the white house and don’t need to be retained). In this case, it seems like he just had his people grab a bunch of boxes that should have gone to the location outside DC and brought them to his “tacky house” (which, LOL! It’s true!), so he could show them off… and possibly even sell them off. Given what seems to have been in there, I’m guessing he was more than willing to sell them to the right bidder.
Because he’s a lazy, incompetent asshole?
I think so… yeah, he’s not particularly smart, but it really doesn’t take a genius to figure out that these documents can be highly valuable to the right people. And he’s long had an interest in foreign affairs, back to the Cold War days… I seem to remember a story from the 80s about him wanting to negotiate with the Soviet Union on our behalf…
I really don’t know if he actually believes that shit or not, honestly, or if he just pushes it for the fund-raising… could be he came to believe it after pushing it for so long.
Oh yeah! And I’m guessing that Kushner was at the forefront of that, too. Because he was eager to work with the Saudis, and promising them some good defense documents would be a great way to ingratiate himself with MBS…
There are still scads of classified documents prepared before the widespread use of computers. Many / most have not been scanned to SIPR and have at best been transferred to microfilm but there are still tons (literally) that are still in paper form. Fun facts!
It’s really true… I don’t know that people have any idea just how much material is in our national archives and how little of it has been digitized. For the stuff I’ve looked at there, none of it was on a computer, but was on paper (from the 60s into the 80s). And we have national archive facilities all over the country, and then there is the Library of Congress…
It’s so much stuff that needs to be preserved for the future, both physically and digitally (with lots and lots of back ups!).
Yeah I think the best way to understand Trump’s actions is to realize that everything he does, he does to feed his own ego. Even more important than making money. That’s why I don’t believe that his motivation here (or at least his primary motivation) was financial.
Take Trump’s entire career as a real estate mogul: most analysts will tell you he would be worth more today if he’d left the real estate empire he inherited from his father more or less as-is and kept bringing in that sweet sweet slumlord cash. But instead he sold off a bunch of lucrative properties so he could free up enough cash to buy casinos and skyscrapers that he could slap his own name on in big tacky gold letters. He was more interested in building himself up as a brand than he was in building a solid financial portfolio. He obviously likes having money, but what he lives for is being in the spotlight.
So while he’s certainly not too principled to sell off national secrets for cash, it’s really not his M.O… He’s the kind of guy who would compromise national security just to impress some of his fawning supplicants.
I don’t think that him wanting to sell secrets is out of the question though… this is not deep level espionage here, it’s realize that our state secrets have value on a an open market… he’s very much able to make that connection, I think, especially if he had people whispering in his ear about that. People like Putin or MBS are certainly smart enough to manipulate Trump into that…
Both can be true.
He does. I have evidence.
