Sad story. Would guess those folks might of needed survival suits to stand a chance on that big lake.
Even on the rivers around here in the winter time I dont think a life jacket is a guarantee you are going to make it out alive. It just means you will be on the surface.
There are other things that should be in place to to help if a incident comes up. Letting people know when to expect you back. Maybe cell phone and lighter in water proof bag. Wear your kill switch cord. This last item is a must if by yourself. Debatable with others in the boat.
Make sure others in the boat know what to do if someone goes in the water. This last precaution is very important if boating with others that are not familiar with being in boats, on the water or even your boat. Takes just a few seconds to point out the boat cushion, rope, how to start the motor, ect. If those in the boat do not know what to do quickly you can easily float away from the boat very fast, out of range of that cushion or throw rope.