As a layman, it’s kind of surprising that they attempted to CPR someone that long in this situation. If I pulled someone out of the water 2h after they went missing and they were cold to the touch, I would probably call the police and wouldn’t even ask for an ambulance.
I believe this is common to attempt when dealing with very cold water drownings. Obviously this is a very extreme case, but I believe you'd generally be instructed on the phone to start CPR but not try to heat them up until the ambulance arrives. Just in case.
The case below had a person conscious in the water for 40 minutes (with an air pocket under the ice) before going into circulatory arrest, and then spent another 40 minutes clinically dead in under water. The combined 80 minutes in the water lowered her body temperature very dramatically, and played a large part in her almost complete recovery.
There's been plenty of previous evidence that cold water immersion significantly slows down the destructive process caused by hypoxia in the brain. I don't think they'd have tried that had the boy stayed in a heated swimming pool for two hours.
Guidance in the UK is that you always attempt CPR with children and continue it until you get to hospital. This is mostly for the family. They have the knowledge that you did everything you could, and when the child is pronounced dead in hospital the family have a lot of support available in the hospital setting.
The article describes their decision making process:
> As rescue divers searched for the boy's body, we deliberated whether to attempt resuscitation and likelihood of meaningful neurologic recovery of a child submerged for at least 90 minutes. We reviewed literature for guidance2-4,6 and drew from institutional experience with a 2-year-old submerged in ice water for 40 minutes who received 101 minutes of CPR.3 The toddler recovered with no sequelae. For our current patient, the decision was made to resuscitate and rewarm the boy because of his young age and protective effects of ice water submersion. We reasoned that if meaningful neurologic function were not observed after rewarming, end-organ preservation on ECMO may allow family goodbyes and organ harvest for transplantation to give other sick children the gift of life.9 This important point should be considered by providers faced with the difficult decision to attempt resuscitation of a patient with asystolic hypothermia >90 minutes.