the real problem is not being investigated!
I will go as far as to say that a take-off in a large aircraft without runway lights is not that uncommon. I have seen it occur at least twice.
With the very effective lights fitted to aircraft these days the absence of runway lights would not be difficult to overlook.
In the two cases I saw, both crews were not aware the runway lights were off during their departure until advised the next day. So one must ask, how many times does it occur with no witnesses on the ground ?? A lot more than most of us would estimate??