One teleprompter speech does not mean anything. It's called sunsetting. Good day/bad days that lead to far more bad days. It's progressive. It started a year ago to get bad. That's why he wasn't doing public appearances.Do you deny that his State of the Union address was pretty good?
Look at him now. It took almost a week after the resignation just to address the nation. And it wasn't live. It had to be taped. And he sounded bad then.
Just admit that he isn't up to it and move on.