Speculation: he may have been wiped, like with a cloth (ie electricity). There’s no there there.
That is an interesting idea. One I hadn’t considered. Makes a lot of sense.
If your brain is wiped, you can’t rat out the other derps.
IIRC, Biden, well before the 2016 election, had a long history of blurting out info that I’ll bet the derps didn’t want out.