Age isn't the issue because there are 90+ year old people still making contributions to their fields. For a lot of people, however, aging past 80 involves somewhat significant cognitive decline. I can cite my parents, aged 87 and 88. My dad was a doctor all his career and is still as mentally sharp as ever. My mom has Alzheimer's and is declining rapidly, though the failing is in her memory, not her ability to complete a thought, like Joe's. We can see the change in her over time, and we see a similar change in Quid Pro, despite them trying desperately to shield him from public view. You thinking that he's fully capable of handling such an emergency as I pointed out is astonishing, to say the least. Someone fully capable does not space out like he does, looking helplessly for a caretaker to direct him. You only have to watch what happened after the debate. TRUMP! turned around and walked quickly off like a man who had things to do and places to be while Quid Pro waited for Jill to come, take his hand and lead him over to the steps, where he paused and did the shaky old man tentative tapping with his foot, looking for the edge of the step.
As for TRUMP!, I am fully confident he would first do what he could to handle the crisis and only later would worry about whether he would benefit personally or not. You only have to look at his first term to see that. He lost money as president, not even taking a salary, something very few have done.