I think it’s the mom’s reaction that escalates it. If she just said “oopsie nbd”, I don’t think the kid would have spilled it all. In for a penny, in for a pound.

As an adult, I can handle being clumsy, like bumping my elbow or my toe, or spilling. But when I’m trying to be careful, and still screw it up I get really mad. Kids just don't have a lot of physical coordination so when they mess up despite heroic efforts, it’s really frustrating. It probably feels to them like they’ll never be big enough and strong enough to do it right. Once you’ve messed it up, there’s not much left to lose.