The answer is simple: Brain addled and senile, Biden doesn't even remember the admonitions of his handlers. They could tell him a hundred times to not repeat these lies, but he 'remembers' them as facts.
You have to credit the demoncrap propaganda media to cover up any misdeeds by a democrat, unless it's a juicy sex scandal.
Then, it's just about sex, no big deal.
“Addled” doesn’t really apply with Biden. He’s been a liar his ENTIRE LIFE. He’s lied about his college record, he lied about the truck driver IN FRONT OF WHOM his first wife pulled out, resulting in her death along with their baby daughter (Biden claimed for years that the driver had been drinking, causing much pain to the driver and his family). He lied about how he met Jill - claimed it was a blind date, but her ex-husband attests that they were having an while she was still married to him. Biden is a career liar. #FJB