>>717081540
>How did she become the most popular umamusume in the West?
She was already the most popular Uma in JP if you look at fanart numbers, so the question isn't "why in the west" but "why is she popular period"
and the answer is she's a hot mad scientist with gap moe of being a surprisingly doting mother to Daiwa Scarlet, a main role in the movie that even got a theatrical release, and general mad scientist shenanigans while also being quite explicitly for (you)