You are right, you can't be prosecuted for using a mobile phone when crossing the road. This wasn't a prosecution though. It was a claim for damages. The court has listened to the evidence from both parties, including an independent witness - who was also cycling at the time - who describes the cyclist as riding aggressively. On a balance of probabilities, the judge has ruled that the cyclist was liable for damages. The judge has also acknowledged that the pedestrian is partly to blame. What you have here is a sensationalist headline drawing in the reader and hoping they'll become outraged by the decision.
I would agree with you, that the Judge has probably (on balance ) made the right decision.