I feel like ARMS definitely benefited from the timing of it's release.
It came out 3 months after the Switch launched where there weren't many games releasing around that time with users wanting to play more games on their shiny new box.
I would be surprised if it sold 2.1 million if it came out now, but I can always be wrong.
There's only 2 races: White and 'Political Agenda'
2 Genders: Male and 'Political Agenda'
2 Hairstyles for female characters: Long and 'Political Agenda'
2 Sexualities: Straight and 'Political Agenda'