I watched a good interview on TV with an experienced pilot regarding what may have been the instigating factor with this incident.
His opinion was that the Air Canada pilots of this plane had likely accepted a 'visual approach' from the air traffic controllers, rather than using an 'instrument approach'. The latter would have never allowed the plane to approach too far to the right of the intended runway and the incident never would have happened.

'Visual approaches' save time, allowing more aircraft that are stacked-up in the pattern to land in a shorter period of time. The air traffic controllers would have asked if the pilots of this plane would accept this type of approach. But, it is ultimately up to the pilots to decide. The 'instrument approach' is always the safer method, especially in the dark!