The answer is that this was a political show, period, and that there was no national security threat whatsoever.
So, your question/statement is ridiculous on its face. You are playing right into their hands and apparently oblivious to that reality point. There is no need to even question the lock BS.
They now have a SS agent or agents they can bring in for testimony that the lock originally on the door was not proper to secure classified information. They can put him/her/them on the witness stand and lead them to say that the lock they put on the door was much more secure than the original lock. That puts some doubt in jury mind that President Trump was not taking proper care of classified documents.