On first viewing, I was inclined to pretty much give the driver the benefit of the doubt but their error does seem pretty clear, tbh. Based on the video, at the point that they actually started to move, the bike should have been clearly visible. Had they actually seen him, they might have simply misjudged his speed. But the fact that they did not suggests that they were not paying enough attention. That said, because of the speed that the rider was doing, the whole thing was over so shockingly quickly. My personal opinion would put the blame around 70/30 or so, against the motorcyclist. His speed robbed both parties of any useful reaction time, that could have averted or lessened the damage from accident.