I don't think that Narain needed to be in that space though. He had a metre or more of track to his left by the time the collision happened. You can see this clearly in the head on stills on the 3rd page of this thread. Narain moved at least as far right as Vettel moved left....To me it almost perfectly mirrors the Hamilton-Kobayashi incident of last year.
Both drivers have made the pass and they both move onto the line they intend to take for the next corner.
Unfortunately there was already a car occupying that space.