It is just popular villains period. All the popular villains tend to be white.
To me, from memory, that is because there are no popular black villains in comics other than Manta. I coulda swore Manta has done some misguided heroic stuff before but I don't follow DC that closely. And that dude is pretty much evil as hell in the same vein as Joker ad Red Skull, so idk if turning him makes any sense anyway.
But yeah... what other actually popular comic villains are POC?
The POC villain gallery is just trash.