David, Biden was left with the only move he could make. Biden is no hero, because he placed all elections in a hole. He and his enablers insisted on his running a second term and made Trump the centerpiece of his campaign, in effect, elevating Trump.
A competition for the nomination would have generated broader excitement than Harris being essentially anointed. But Biden delayed almost a month after his implosive debate.
So far Harris has performed well, but she has a formidable task ahead of her. Her choice for running mate will be critical. It must identify her in a positive way. Going with an old white governor will shoot down her current balloon.
Buttigieg would be an excellent choice because he can really help Harris.
Best.