RyanAir Child falls while boarding plane

On RyanAir, a small three year old child named Olga was walking up the steps unescorted as her mother was holding her 18 month old brother and handling their luggage as well. She turned around to speak to her mother and fell in the gap between the plane and the ground, landing on the tarmac below. 
The child was flown to a hospital, where she was released 24 hours later. 


Details here. 
I have a question. Have you ever looked down at the distance between the ground and yourself when you are on the stairs or jetways between the plane door and yourself before you step over? Sometimes, that distance can be high up. A wrist strap broke on a camera of mine, and the camera plummeted to its' demise. The only thing I was able to retrieve was the memory card. 
Why on earth would you allow a child to travel the same jetway or stairs without holding a little ones' hand? 
I do not care how much you think you need all of the things that you are bringing on board the plane with you. If you cannot hold all of what you are bringing on board, wear it in a small backpack. 
Small children are allowed to board with their families early so that they have a little more time. 
I am still baffled by this as I do not understand how this mother could have let her child walk up that stairway to the plane without holding her hand until that tall threshold between the plane and the stairs was crossed.