I understand the racial aspects, but I would have voted for Minnelli. I thought she was sensational as Sally Bowles and made it her own compared to the Broadway versions. I also love Bob Fosse's work in Cabaret. Liv Ullman is one of my favorite actresses. Tyson was great but it felt like a supporting role. Tyson is a sensational actress. I saw her on Broadway just a year or so ago with James Earl Jones in The Gin Game and at the age of 90 she was as energetic as any young performer. She projected well and blew me away.
Yeah true, Liza was fun to watch in
Cabaret. She kinda played herself, but sure she's talented and the role was kinda taylor made for her. Plus, it was the perfect opportunity for Hollywood to in effect pay homage to Liza's mother, Judy Garland, who had missed out on winning the Oscar in 1955.
I believe 1973 was the first time that two African-American female actors were nominated in the leading role category in the same year. No matter the amount of her screen time, what Cicely Tyson accomplished in
Sounder is searingly memorable to this very day. Tyson is one of the greats. There have been roles like that portrayed by other actors where the screen time is not huge, but the acting chops in those indelible moments light the scenery on fire.

Diana Ross sunk her teeth and indeed her entire body, soul and emotions into playing Billie Holiday in
Lady Sings the Blues. Some might feel that Ross was a bit overdramatic, but I felt she mostly hit all the acting notes (as well as the singing notes) just right, surprisingly and revealingly so for a singer who did not strictly have an acting background, somewhat similar to the winner, Liza Minnelli. Many felt the win would come down between Liza and Diana, but nope, it was always Liza all the way. And Liza was certainly good as well as in good company with the
Cabaret cast, as well as with her fellow nominees. It was not a surprise that Liza won. She was good enough for there not to be many, if any, cries of Diana Ross being wuzrobbed.
As far as "racial aspects," eh that's just a faux term. It's about systemic bias related to the history of humanity. It's at the very core of a lot of things that are still present with us in our culture. There are no different races really, but we can't escape having to use the terminology that's simply a destructive manmade construct. Lena Horne, Butterfly McQueen, Dorothy Dandridge, Ethel Waters, Beah Richards, Diahann Carroll, Diana Sands, Ruby Dee, Cicely Tyson, Angela Bassett, et al... Halle Berry was humbly crying a river of tears in honor of all these ladies on Oscar night in 2002.