Biden is mentally compromised for sure and certainly in early stage dementia
He knows what is going on.
He knows he is in decline and that his time is short.
He is and always has been a sociopath who gets off on screwing people over and watching the world burn.
He just wants to feel the power and take as many down as possible before he departs the scene
I think you have a valid point. On occasion, he can sort of answer a few questions, which indicates he still has some comprehension of what is going on but otherwise Soli relies on notecards and teleprompters. If you tried to get him off-topic, By asking questions on related to watch the speech was about, I suspect he would have a much harder time answering.