Quickest way to determine if this is true is to FOIA the documents.
The issue is that MAGAts will just plug their fingers into their ears and yell "LA LA LA, I can't hear you over the sound of DJT declassifying those files!", irrespective of the truth which is that Trump did NOT have the power to declassify those files. It's literally the whole "I had the largest Presidential inauguration" all over again; even though the facts are laid out in front of some people, no matter how clear as day as they can be, those folks will refuse to accept the real facts but instead push "alternative facts".
Honestly, the time to convince those folks is dead and gone. If DJT said the sky was purple, his followers would believe him and no one could convince them otherwise. You literally cannot convince people out of a position using logic if they did not use logic to get themselves in that position to begin with. I say the FBI needs to press any and every legal charge they have against Trump and his cronies because breaking the law has consequences. It doesn't matter whose feelings get hurt. Actions have consequences.