I can't agree with you on this. Your view of mental illness is crude at best, but even so, Trump comes pretty damn close to your description of what it would be. He really truly believes that the election was stolen from him. It's not an act, it's an extreme defense of ego and he can't help himself.
What makes him an extreme danger is that there is so very little volition and that he absolutely does not have control of his impulses. His entire psyche is built around a delusional self-image of his inherent superiority. He MUST have won because he is obviously superior and so many people love and admire him. The only way he could have suffered a humiliating loss is if it was stolen from him. And Pence absolutely had the ability to stop this theft, but chose not to, so he betrayed Trump.
He is at his most dangerous now because all his props are disappearing. The immediate gratification of Tweets to his adoring audiences is gone, he's facing censure from the media and , the loss of the PGA, the loss of his merchandizing platform. The hits just keep coming and whenever he's cornered, Trump fights back with force greater than the injury delivered. The greater the threat to his ego, the greater the violence of his reaction.
He's always been unhinged, but he's had people to buffer him and shield his outbursts from public view. He's cracking up now, worse than ever. The 25th amendment is absolutely appropriate -- conceptually -- even if it is not the most politically expedient at this time. That could change in an instant.
Having thought it through a few times, I'm with Beebo on this.
While I am certain the 25th Amendment was written to cover circumstances where there's doubt the President is out of commission -- he's had a severe stroke or heart attack, say, or is in hospital after an assassination attempt -- in theory it should also cover circumstances in which the main problem is that the President's judgment is so impaired, for whatever reason, he can't safely be trusted to discharge his various duties and responsibilities.
That's because, if the president announces that the voices in his head have told him to nuke somewhere, or he's hallucinating, then the VP has to be able to take over at least until the president has recovered.
Under those circumstances, the VP and secretaries of state wouldn't have to wait for a formal psychiatric evaluation -- they would form the view that he was unwell because his judgment was clearly impared, sign their letter, and do whatever needs to be done to make the take-over a fact.
While I'm not at all sure how they'd go about telling him Pence was relieving him of his duties, it seems to me clear that if they've formed the view that he's incapable of performing his duties because his judgment is so badly impaired there's no alternative, then it's their duty so to do.
However, under the present circumstances, I think impeachment would be the better way to remove him, since it's an equally applicable remedy for the actions that would also justify using the 25th Amendment, and one that seems far more appropriate, since the evidence he's incapable of governing is the behaviour for which he should be impeached.
ETA