I have several pictures I haven't uploaded yet from my trip where that was done, the light was mounted above the first set of high voltage wires. It seemed quite dangerous to me, maybe here some people complained about too much light shinning into their windows across the road and they decided lowering the light was the best option. I can also see why they didn't remove the arm.
Probably would require turning the power off, and they did not want to do the leaflet drops and come back in 2 weeks to do it, might be scheduled for routine line maintenance time in the near future.
Maybe the light had something wrong with it. The longer arm is probably so more light gets thrown on the road. When it was higher the light casted further so they could use a shorter arm.