While on paper keeping the investigation secret might sound like a good idea, in this environment it is a terrible idea, as was taking the passports. The Federal government has now lost all credibility with about 50% of the population. That 50% was the prime recruiting territory for the military and provides the middle/working class backbone for the US. At this point, the government's only method of persuasion for this group is coercion. Any outcome now will be viewed as fraud and 3rd world politics.
But "the military fully supports Biden", as Telmar once claimed.
But it does not really matter, because the whistle has been blown and the dogs are barking. It does not need much to have them barking, just throw and jingle a few "trigger words" and let idiocy do the rest.
Classified documents! Oh! That's scary!
Top secret documents! Oh! That's scary!
Documents about "nukes"! Oh! That's very scary!
Trump! Oh! orange Man bad! Everything Trump does is bad! Trump bad!
Classified documents? Ok, what is a "classified document"? What makes a document a "classified document"?
Top secret documents? Same questions.
What are the processes around these documents? Is it common for a former POTUS to have these?
What is the process around the declassification of documents?
Nukes? What are we talking about? Weapons? Civilian energy? Gadgets? Projects? Random, inconsequential, memos?
People can't answer these questions. They don't even ask these questions to begin with. And they don't care about the answers either.
All that matters is that "Trump" factor.
Trump is involved, therefore it is bad. Because Trump is bad. Everything Trump does is bad.
No need to look any further, or ask question, or anything.
Why? Because Trump.
They get their news and pre-digested from twitter, facebook, reddit, etc... from "checked" individuals who have no more actual insight on the subjects. And it is enough for them, because they found lots of people who "think" like them. Safety in number.
Unfortunately, these brainlets have 0 idea how the system works.
In short: Trump has the constitutional authority to declassify anything he wants.