I realize that this is being translated from technical speak to layperson by someone that doesn't know anything, but sounds like a multimeter would've been useful.

I wonder if they got their phases swapped, so when they turned on the breaker, they shorted the opposite phases together. That would probably require a new breaker (as well as clean underwear for anyone near by).

It seems fortunate we get to look back and laugh at this.... This level of misunderstanding could kill someone.