I hardly think he deserved life in prison for what was essentially an accident. He was driving under the speed limit, he wasn't drunk, and the guy he hit was legally over the limit at 0.11 and passed him on the right side driving a scooter. If he had remained at the scene of the accident it would have made no difference in the tragic outcome as the victim was killed instantly and he would most likely have faced no charges at all.
The guy panicked and ran. The only thing he is guilty of is leaving the scene of an accident and that is what he was sentenced for. If he was speeding or drunk, then I'd support a charge of vehicular manslaughter but he was neither while the deceased was both drunk and driving dangerously. Sentencing him to a prison term wouldn't change anything. I have no problem with the judge's decision.