Dairyground, your assumption about the lights is reasonable.
However, this is Johannesburg. It is quite common here to see streetlights burning brightly during the day when they're not needed instead of at night when they are needed.
Even if the streetlights do burn at night, often something with their sensors or timers goes haywire after a storm or prolonged rain and they don't switch on at all, or they come on at odd hours.
If memory serves correctly it had been a wet weekend when the incident occurred. Though it might not have been raining at the airport at the time, it was raining in other parts of the city.
The erratic nature of Johannesburg lighting coupled with poor weather conditions may have been contributing factors.