Scapegoating.
My guess, it was tripping the GFCI so they just disabled it....
I thought pool lights were a low voltage DC circuit?
How ridiculous, having several pools myself, all the lights have been low voltage 12volts. Most pool owners will notice the transformer over by the pool equipment.
Was there some kind of bleed over from the high voltage side to the low side, incorrect wiring?
GFCIs are sensitive - for a reason. I once had a customer when I was an electrician that had an outlet in the dining room that kept tripping (it was protected from a GFCO in the kitchen). Just a bare receptacle, but always tripped the GFCO. Turns out it was under the window that the cat used to look out and see dogs/cats outside and it was marking its territory. Just happened the outlet received the brunt of the marking spray.
Changed out the receptacle and problem cured. The lady wasn’t too happy with the cat, though.