Some fascinating stuff contra "conventional wisdom" from these ongoing studies they looked at. Like this for one example:

In an interview, Terrance Woodbury of HIT described younger Black voters as having “systemic cynicism” towards institutions like the Democratic Party.

“There is a level of disenfranchisement and disengagement,” he added. Woodbury also argued that some of Trump’s messages have resonated with younger Black voters in particular. In focus groups, according to Woodbury, younger Black voters often mention the criminal justice reform bill that the president signed into law, his support for increased funding for historically Black colleges and the low Black unemployment rate before the coronavirus outbreak.

These differing views among Black Americans may not just be about age. When looking at all Black respondents (not just likely voters), Biden had more support among Black voters who were college-educated and those with higher-incomes, according to the Nationscape data. So it might be that more established Black people (older, more educated, higher income) are more satisfied with the Democratic Party than other Black Americans.