I had the idea that it was going on since the 70s or 80s in my head, but I don't know where that came from. Maybe the general attempts to connect black power with an idea that Egyptians were black? It's hard to google this right now because the Netflix series brings up so many hits.
I also now remember that the reason that the BBC didn't cast a black actor in the 1981 TV Othello, using Anthony Hopins in brown makeup instead, was that they had to use BBC actors only had one black person who could plausibly play the character, and he was doing something else at the time. They used alot of RSC people in those productions, so I assume they mostly or all contractually available to the BBC, I just know that James Earl Jones was nixed as someone they weren't allowed to hire. Anyway, I doubt that they had a better track record of hiring black women then black men.
My point still stands to some extent, which is that it's popular to hire black actresses to play Cleopatra on stage. A Netflix series is going to attrack more attention then an RSC production.