dementia...just a natural loss of stamina due to his age...and I agreed with him dropping out of the race.
For over twenty years, my wife and I, along with many other couples and their kids have visited nursing homes at Christmas and seen those who are simply old, and those who are afflicted with dementia...there is a definable difference. Joe Biden doesn't have dementia.
As for Trump...his Off-the-Charts Malignant Narcissism causes him to constantly have to deal with massive insecurities, which he tries to fend off with rambling speeches that can involve all sorts of perceived threats to his "Image" as a "Stable Genius"...hence the wild and crazy "MIT, Sharks and EV Batteries" speech. In short, as Rex Tillerson, former CEO of ExxonMobil, said...DT is a "Moron".