Please. It was the tradition until very modern times for white actors to play Othello in dark makeup as either black or Arabic. Olivier is only one of many actors to do this. Probably had to do with a lack of black actors capable of essaying the role in those days. It is considered one of Shakespeare's 2 or 3 most difficult parts.
Also, Olivier more than almost any other performer in the role emphasized Othello's blackness. Many Othellos before Olivier simply played the role as a guy who happened to be black. Olivier stressed Othello's alien-ness among the white population. He also played him as a Muslim who had allowed himself to be Christianized, and as the play progresses he seems to slip into a more barbaric mindset. At the time, Olivier was criticized by some for the performance, not because of black makeup (which was the norm) but for making such a big deal out of Othello being black.
For me it is one of the few performances of Othello that really works. The white population of Venice may feel racially superior to Othello, but they need his military prowess so it is amusing to watch as they basically kiss Othello's ass so he will protect them. We need to see Othello as a valiant eloquent warrior/lover who has no equal in Venice. That way his fall as engineered by Iago is like a giant tree or tower toppling. It doesn't work it the actor playing Othello just plays him as a nice black guy. I thought Laurence Fishburne would be a good Othello, but I felt he did little with the part. Just played him as a good-looking black dude.
It's been awhile since I watched Olivier's Othello. The last time I did, I was struck by how over-the-top Olivier was in the role (it's basically just a filmed play with theatrical acting). But as it progressed, I had the same reaction I had since I saw it in a theater on a big screen. I started to feel that I was watching the complete breakdown of a man and felt by the end that I should not be there to see what should be a private moment of collapse.
Olivier’s dark face performance in Khartoum as the Mahdi at first seemed over the top but as the movie progressed the inherent fundamental Islamic madness of the character was more clearly delineated in his excellent performance.
Apologies for use of hyperbole to make the point. The word "Even" before "Lord Olivier" was intended to convey utmost respect. "Cringe" was the hyperbole. Although his acting in films was sometimes, as you stated, over-the-top for that medium. Richard Burton in an interview once stated that his wife Elizabeth Taylor taught him to pull back and be more understated for film. Olivier, the greatest stage actor of his generation, never seemed to adapt completely to film. Just my personal opinion.