Good points.

From my reading of the news reports at the time it seems that the three miners descended the main shaft in the cage to a level that had been flooded, unbeknown to them. They were trapped in the cage underwater but managed to open the door and get out in an attempt to save themselves. They did succeed in getting out but apparently the water was very cold and they simply could not survive in it for very long.

Of course, all of the above is only conjecture on my part based on newspaper reports available at the time of the accident.