Can’t give you figures, but it’s a widespread view, especially among road safety organisations, that drivers convicted of traffic offences, especially with death or serious injury, get off lightly. The theoretical maximum sentence is rarely applied. For instance, for this offence (causing death by careless driving) the sentence is often a large fine + a few years driving ban. Also there’s often a plea bargain in which the prosecution of the more serious ‘causing death by dangerous driving’ charge accepts a guilty plea to the lesser ‘careless’ charge. (I seem to remember this actually happened in this case, not sure.) Juries also seem reluctant to convict (’there but the grace of God..’ mentality, it’s assumed.)
Regardless of the harm caused (death in this case) and absent any political angle (such as resentment over diplomatic immunity), I imagine that juries find it excessive to send a driver to prison for simple negligence with no aggravating factors, just a momentary mental lapse. Now, if alcohol, drugs or extreme speeding were involved, that would be (to me) an entirely different matter.