People don't get this but the entire classification system is done under the authority of the president. Legally, the president alone decides what is and isn't classified. Of course one person can't do that so he delegates that authority to thousands of people under him. But it's literally impossible for the president to mishandle classified information because he's the sole authority on it. If he goes on TV and start spilling Top Secret info, that just means he has decided to unclassify that info and that's his right and no one can do anything to stop him.
It's just... never been a issue before.