He has convinced himself that this really happened. Has he been checked for early signs of Parkinson’s Disease? This is common with that disease.
Dementia also, Things get mixed up, stories are told out of context, elements of three different stories get compiled into one, proper vocabulary use gets jumbled. But no matter how mixed up it gets from reality, there is absolutely no way they can be wrong in their own mind. From watching Biden I have noticed a lot of similar signs to what happened to my Dad as his dementia began and advanced. And it wasn’t slow either, within a year and a half it advanced to full blown dementia.