Ah, interesting hypothesis... that Biden is the political equivalent of Vincent “The Chin” Gigante, the bathrobe-wearing mafia don who pretended to be a senile old coot to avoid prosecution? Yeah, um, no. It’s a funny idea, but Biden’s ego is too big to diminish himself intentionally. Biden really is just a senile old coot.
I don’t think he thinks he is lowering himself by pretending to be ill. I think he is an actor and delights in duping people. Especially people who think he is stupid for having low marks and being at the bottom of his class. He is clever in a wily way. Duping and lying to people makes him feel superior. And he gets the sympathy vote from many people for his apparent illness, an illness which nobody really knows for sure. So I think under it all he gets a chuckle at the stupidity of the American people.