Dementia may be complicating the picture, but Trump has met full criteria for ADHD since childhood. Many of his political strengths and weaknesses stem from this condition. His followers love that he he "goes with his gut" and calls it like he sees it, and blurts out whatever is on top of his mind, without filters, mistaking his candor for honesty. His tendency to perseverate on certain topics, and to ignore what is important for what is of interest to him were hallmarks of his presidency. These articles from over a year ago addresses some of these points, and I go into more detail in my book: Recognizing Adult ADHD: What Donald Trump Can Teach Us About Attention Deficit Hyperactivity Disorder. https://medium.com/politically-speaking/consistently-inconsistent-trump-45fa8f2f589a

https://medium.com/politically-speaking/trumps-conceded-trump-s-conceited-9be7acf4a3f1

https://dockruse.medium.com/can-we-talk-about-donald-trumps-adhd-now-764ec019db82