A common symptom of Alzheimer's/dementia is loss of inhibition i.e. saying things you'd otherwise be guarded about. That's why he's constantly confessing things in front of the camera - voter fraud organizations, Ukraine quid-pro-quo, etc etc. It's also why he constantly says racist shit like "You aint black".

When you lose your faculties to dementia, you forget that you're not supposed to say that stuff out loud.