Trump's Keeping of Classified Documents Related to Iran Attack Plan

There's some existence of an audio in which Trump says he kept classified documents related to a plan to attack Iran. The document was General Mark Millie's write up of his plan for attacking Iran, which it looks like Trump may have turned down several times. Why do you think Trump would want to keep that document with an Iran attack plan? Of all the things he could keep, why would he want that? I have a theory because it makes Mark Millie look like the dumbest guy in the world and a warmonger who's going to get you all killed.