Bairstow
Well-Known Member
He doesn't build his own robot. Baymax the robot was built by his older brother as a medical assist unit. When the older brother gets killed, Hiro seeks to avenge his brother and upgrades Baymax into a battle unit.
And you're forgetting that there are 4 other characters in this film that probably made Disney pick it, including a guy that can turn into a giant Godzilla-type monster.
You're assuming they're keeping the same backstory.
Disney already showed that they're willing to change the kid's name, so don't be surprised if they switch other things around too.