It was very much not a proper server room, which made it more understandable that they'd not realise there was stuff there that shouldn't be turned off.

I suspect there's been plenty of real-world incidences of stuff like this, and that many have never been noticed.

I've certainly pulled the wrong cable myself a couple of times over the years, even after thinking I'd been very careful, and being aware that I was dealing with servers that should stay up.