Ilek, I don't think the judges saw it that way: there is only a 0.25 difference between Mirai's and Liza"s IN scores and and a .20 difference between their P+I scores.
What's wrong with Mirai? She doesn't look like she likes skating at all I think both hers and Elizaveta's PCS were too high. For example compared to Isabelle's(5 points lower) who skated a clean program with good jumps/tech and no GOE minus. OK you can do a lot of transitions, but what's with that if you pop jumps/UR them/fall…?
Julia and Vanessa nice surprises
I don't think Mirai didn't care, but I think she was trying to appear light/carefree, to fit the music. You can tell by her body movements that she was definitely committed to the choreography, but her facial expression didn't work with the music as noted.
There is some music for which smiles are inappropriate.