More likely, he's reaching the end.
His handlers are on borrowed time, and they know it. Dementia has a few 'stages' we could call them, clear points of behavior that occur across cases. Right now, Biden's at the point where his memory is swiss cheese. Massive holes throughout. BUT, he's able to rationalize them in most cases, connect entirely disparate events into a narrative that he feels makes sense. The human mind has an amazing ability to try to make sense of nonsense.
But there is a limit on that.
Once that limit is reached, once they realize things don't make sense, they lash out and get angry. Increasingly desperate rationalizations inevitably converge on "Everyone is working against me". It's the only explanation that makes sense to them. Keep in mind, they aren't forgetting everything day to day. Its more like bits and pieces remain and they need to string those pieces together into a seamless whole.
The usual method of dealing with this is to try to make things how they expect them to be, to change as few things as possible so that the stitching process has to do less work. That is not an option here though, the Presidency requires too much change, to keep track of too many factors. The handlers thus have chosen to sequester him... but he knows he is President. So there is one question that his handler's have to ask themsleves.
What happens when Biden can no longer rationalize events? Or in other words, what happens when the President decides everyone is against him, and acts on that?
Right now, the handlers hope is to keep him propped up for 4 years until he can politely refuse to run again. The thing is, the man's decline is rapid, too rapid. He'll be lucky to go 2 years, let alone 4.