One theory is they live more people to a house, most often a cultural thing.
Because they are together they are exposed to a higher viral load and therefore get sicker. Someone who is exposed to a smaller viral load often times won’t get as sick.
Another theory is that, based on what I see on TV in DC and neighboring Prince Georges County, the percentage of people engaging in block parties and other social events involving hundreds of people in very close proximity leans very heavily toward “People of Color”.
Paraphrasing Carville,
“It’s the behavior, Stupid”