Why is Joe Biden whispering?

I first learned about this on the Colbert show. Joe Biden was doing this bizarre thing whispering at a press conference.

I like Joe Biden for a variety of reasons, but has he lost his mind?

A quick google search found lots of talk about it on the internet, in case you haven’t seen it. I tried to find a link that wasn’t too right-leaning, so take a look at this one:
https://www.msn.com/en-us/news/politics/freaks-me-out-biden-s-whispering-splits-the-internet/ar-AALrueg