Really, you would let a 4-year old run through the entire museum with their hands behind their backs? Not just because they’ll fall flat on their face when they trip. That is one weird parenting method, right up there with things like time-out, more akin to dressage than nurture / education.
This. While we don’t know why exactly the father didn’t watch the little fellow in that moment when there were artifacts in his reach, he should have.