It's not a theory that the FBI has conspired to fabricate evidence against Trump, so what you suggest is not outside the realm of possibility. If there was an inventory taken before the documents were stored, that should make it pretty easy to tell if anything was planted.
We're at a point where we are forced to choose what seems more likely. Either Trump is who he presents himself to be, a DC outsider who puts America first, or he is controlled opposition, putting on gargantuan revenue generating theatrics for the masses to consume and be placated.
The third option, that Trump is looking to overthrow the government and establish himself as dictator (or whatever of the various shades of that fantasy) has never had a remote possibility of being true. I can't imagine how anyone, after being lied to so many times, can continue to even entertain that idea, after all the lies being repeatedly exposed, over and over. People just keep going from one lie to the next, never reflecting, never looking back and challenging how they process information.