I've wondered this myself. Some days he sounds sharp as a tack. Others he slurs so much he doesn't sound coherent. But he evidently soils himself and supposedly did so with the Pope. Biden is just awful enough to make one wonder if he did it on purpose.
Truly, who knows if this is true? Everything word written by the media is a lie, or at least a lie by omission.
I don't think Biden is an Einstein by any means, he seems to me to be more crooked than smart, but there's just something a little off about the "I'm a feeble old man, be kind to me" facade.