One thing that I think helps Mikey Madison's case this year

Looking at the website Screentime Central (compiled by the incredible Matthew Stewart), I saw the stats for Best Actress last year. Emma Stone had 1 hour and 37 minutes of screentime and was in 70% of Poor Things, while Lily Gladstone had 56 minutes and 13 seconds of screentime and was in 27% of Killers of the Flower Moon. The Oscar went to Emma Stone. This year, Demi Moore is in 59 minutes and 42 seconds of The Substance, and is in 42% of the film, while Mikey Madison has 1 hour and 49 minutes of screentime, and is in 79% of the film. It seems like voters are gravitating towards performances with higher screentime who don't share the screen with any other co-lead and create more memorable impact in their film. Demi Moore is phenomenal in The Substance, but a lot of people find Margaret Qualley's campy moments more entertaining. When people walk away from Anora, all they think about is Mikey Madison's performance. Also, Best Actress has recently gone to women who are the sole leads and dominate the screentime of their films; the only recent exception is Olivia Colman for The Favourite.

Or maybe I'm just overthinking this and it was Demi Moore all along and it's not even particularly close.