i watch a few times, Merc was at the saab blindside, saab drift in instead of cutting in, merc probably though the saab should have seen him and will stop, but the saab just kept drifting into the merc...maybe saab driver never saw the merc (blindside), thought the merc was further back and will slow down when he drift in....
its like those cars drifting into another lane while avoiding a bicycle, without checking their blind side, only see side mirrors,
if merc blocking, one will drive ahead and drive side by side, certainly not at their blindside.
or if saab cutting, it would be like when the saab cut in the car behind, not drifting into the merc