Biden answered the question he wanted to answer (How is Trump doing?), Politicians change the question all the time. Trump does it every day. The problem is Biden has lost the ability to make the transition from the asked question to the issue he wants to talk about.
He just staggered mentally right into his planned statement without the usual “What’s really important is, etc.” part.
The other problem is Biden seems to have speech trouble often seen in stroke patients. I think he knows what he wants to say, but the words won’t come out right when he speaks. If I’m right, this makes him sound worse than he really is.
My aunt has cognitive problems and that happens to her, she try’s to say something but just can’t get it out. I notice a Biden is having more trouble with that.