Change the word 'ride' to 'drive' and you have just given a perfect excuse for every bull headed driver out there.
If you choose to prefer the guilty getting off scot free then go right ahead but here in the real world murder is a difficult thing to prove in almost every case. It involves, as said above, proof of intention to kill not injure not frighten not maim not cripple but KILL. Such a thing would in this case be impossible and the case would simply have collapsed. If you wish to blame all drivers for everything [as many seem to do] then imagine the case of a cyclist taking a shortcut along a footpath and accidentally hitting and killing an elderly man. Clearly a criminal [he was on the footpath - breaking the law] and hit an innocent pedestrian by your reasoning it should be murder.
Just to be clear, attempted murder is the charge which needs proof of intention to kill.
Murder can be proved by the intention to cause really serious harm and, of course, the subsequent death of the victim.
@sidevalve's point still stands, the intended harm must be really serious, a slow speed mowing down of a cyclist would not be enough.
Many on here may think it should be enough, which is an argument for a reform in the law, but the law has been applied correctly in this case.
The recent 'love triangle' murder trial of Cohnor Coleman turned on this point.
Coleman killed his victim by battering him about the head many times, but the jury still acquitted him of murder.
http://www.bbc.co.uk/news/uk-england-york-north-yorkshire-34616177