The most likely reason for a cameraman to react like that is because that kind of performative amazement is what mammalian brains like to see and feel. Think about how many completely unnecessary “omg”s and “Really? Are you serious? No way!” You hear daily.

You’re not wrong that realistically, if 250 is the weight cap, it shouldn’t be surprising that someone brought a bot that weights that much.

“Wow, this purpose-built machine meets the requirements to enter this competition? Are you being real with me right now or are you pulling my leg. I was not expecting this thing to weigh as much as it should to get in.”