Black Snape really is really fucking dumb, there are way more characters that they could have made black where it would have been fine, but no they took one where it was the least fitting.
Maybe WB thinks this will absolve them of funneling endless amounts of money into Rowlings pockets?
Yeah, they could have made Voldemort black.
Or Sirius? Sirius Black? Clues in the name!
I don't actually think WB really understands the whole issue.
This casting feels way more like some kind of black washing tokenism that would have been done in the 80s or early 90s.
Like when a random black friend is established as part of a friend group, even though said friend appears to be from an unrelated background to the main cast/group, with no real explanation as to why they are there, other than to be black.
Usually they probably would have been originally written as just one of the gang, but as no one was actually thinking about the color of the characters, then they wouldn't specifically think if one is black or not.
Either they would be used as a vehicle to "explore" storylines about racism and that was basically the extent of their character, or the fact they were black was never mentioned and their presence made even less sense.
JK pretty much did similar things in Harry Pothead in the first place anyway, Cho Chang and the Indian Twin girls were kind of shoehorned in, but again, getting back to the British boarding/public school environment, it was a tad more common then for kids of Hong Kong Chinese or moderately wealthy Indian extraction to go to those sorts of schools.
The girl who winds up being captain of the quidditch team, she was played by a black girl in the films and strongly implied to be west Indian in the books.
As for black Snape;
I am hoping that this is some kind of misdirection and this guy is actually playing a different character, but WB or JK thought it would be funny to troll audiences until the first episode.
Or, this guy actually winds up playing a pretty amazing Snape. It could happen!