Biden got 92% of the black vote because he promised progressive policies.They are leaving him because he went from promising police reform,student loan forgiveness,medicare option for all, criminal justice reform,voting rights etc to fund fund fund the police,border security,bragging about the 350 million he gave for more police,the highest military budget ever,no mention of climate change,healthcare,student loan forgiveness etc.
If blacks wanted conservitive polices Trump would have got more than 8% of the black vote.