The most detailed information was in the interview with Peter. The safety put in place seemed not to be too bad - a guiding line and lanyards, multiple escape holes, scuba and freediving safeties. From what I understood, the victim was not very confident with himself about doing it to the 50m hole, and was advised to wait for escort. It was not written whether he ought to be escorted by a scuba diver or by another freediver. However, either he did not understand that (because of the hood), or decided to go anyway. Allegedly, a freediver from the 50m hole went to meet him at 20s after the immersion. When he did not see him, he came back (at 40s after the top) and a scuba diver went to search him. It is not clear whether the scuba diver was waiting on the surface, or whether he was on the way back from the last hole (125m?) after escorting Peter. I believe there were more scuba divers, so he was probably not too far. They found the victim easily (he was attached on the lanyard) and brought him to the surface at 2:45 after the top, and started the CPR.
Now, l can only speculate, since I know just the few details published in the interview, and in some other reports, but from the few details we know, it looks like the guy got into troubles very early after the immersion - otherwise the freediver who went to meet him would have to see him. From the times published, I'd tell that he had to search him at least some 10-20m back from the 50m hole. I do not know what visibility was there, but it could have been some additional meters, so it looks like the guy blacked out before 25m (my speculation only, not a fact!).
What is also strange, is that he died despite been rescued very quickly. Being 2:45 under water, and especially in cold water, does not sound too bad. I also understood he was stabilized during the CPR. I do not know whether they used oxygen immediately, but wonder whether he inhaled a lot of water and whether secondary drowning could have been the death cause, or whether his health complications were not the real root of the tragical end. I definitely hope we will hear the results of the investigation later.
It is also a question why he blacked out so early. Either he was under big stress and fear and hyperventilated more than usually. Together with the harder conditions (altitude, cold, thick wetsuit, weights, physical effort beforehand,...) he might indeed have an early BO shortly or just after the immersion. Another possibility again is that he had a health problem. Or perhaps something went wrong during the CPR and/or transport. Perhaps improper methods were used, but that's a huge and rather improbable speculation. Though, it happens too, so it can't be excluded.
The safety and the rescue were much better that it was the case a year ago, at the accident in France. In that case, they only found a freediver is missing practically at the departure. And since he had no lanyard, it took about a week of intensive search by police divers before they've found the body.
So if you plan organizing an event under ice, you have to count even with cases like this one, where the freediver due to the harsh conditions and heavy stress, or due to health complications, can black out just after the immersion or any time under the ice. On my mind lanyards are the absolute must, and the diver needs to be monitored from the moment of immersion to the surfacing - either by a scuba diver, or by a more experienced freediver, or from the surface (if the ice permits it). Having a reliable and freezing-proof and tested CPR incl. oxygen on the surface is certainly very important too. Equally important should be briefing, and a rigorous buddy system.