Was harris picked to be vp because she was the most qualified person or was it because she was a woman and biracial ?
Was biden picked becasue hes da man and the best qualified or was it simply because he was not trump ?
On the choice of Harris, I think you nailed it. Add to that, the fact that, as powerful former Cal Assembly Speaker and former San Francisco Mayor Willie Brown's former g/f, the DNC can say they did him a favor, or paid him for his past loyal service to the party.
And I think Harris impressed them with her ability to cow Biden in that debate.
I think Biden was always their preference, but they held a tournament (the Primaries) to see if someone else might stand out as superior to Joe.
His attractive qualities are that:
He is likeable.
He can be outsmarted by Obama, and that means he is controllable without using outright blackmail. He is their puppet.
He knows the system.
The public had, and some degree, some STILL retain, a false positive impression of him as a nice competent guy.
There is some degree of sympathy he benefits from as many people have 1st hand experience with parents or other loved ones who have suffered mental/physical decline due to age, injury or infirmity.
He is vulnerable to the threat of criminal prosecution on several different types of offenses. Sexual. Treason. Business. Government corruption.
It seems the DNC used Joe Biden as the model to help fashion the arsenal of weapons used to poison Trump's reputation.
The word among most Trump haters was/is that Trump was supposedly stupid, decrepit, inept, incompetent, a sexual predator, a crooked, disreputable, dishonest liar who had never accomplished anything of significance on his own.
To anyone who knows Trump and Biden, they would say those characteristics only slightly and vaguely describe Trump.
But they PERFECTLY fit Biden.