We're discussing hypotheticals. I haven't diagnosed anything either. Hypothetically, if Trump as a personality disorder, then that will prevent him from making rational decisions.
He wasn't voted in to make rational decisions, he was voted in to make the decisions that the people who voted for him want.
For example, there's nothing rational about supporting the American coal industry. Coal's time is past. However, Trump's promise to rejuvenate it was key to him winning the election.
The difficulty would be that it might look as though he was doing his job, just screwing it up, when in reality he would never be mentally capable of doing his job at all.
If Trump is mentally compromised to the point that he is unable to perform his duties, then article 25 should be invoked. However, we don't know if he is or not. What the USA needs is a way to get rid of a president before his or her term is up if they are really just very bad at their job. This is why I was interested to know if LR has any ideas how it might be done, but it turns out she doesn't.
Most US state governors can be fired before the end of their term by means of a recall vote. Perhaps something similar needs to be instituted for the president.