There could be a lot of reasons for that.
For example:
Evidence suggests the demographic age structure of sub-Saharan Africa is the leading factor of the low morbidity and mortality of COVID-19 compared to other regions of the world.
or
Studies from developed countries have demonstrated a higher risk of death in racialized communities, including those of African or South Asian descent.
15 This predisposition is likely related to socioeconomic factors including poverty, crowding, and working in essential services. Therefore, overall environmental exposures are likely far more important than genetic exposures in disease susceptibility.
How is arbitrary if the evidence shows those racial communities in the US DO have worse Covid outcomes regardless of the reasons?
It takes a lot of time to figure those things out. Like years. In the meantime you have to treat people.
We are, look at tbe article I linked to. That is just one of many.
Treating the actual issues is a hell of a lot more complicated and politically charged.