Cross country was designed to be galloped, in australia it is usually 700m per minute they cover. I am sure the rider who's horse died was an accident, yes maybe she misjudged the distance, it happens to the best of us.
I am sure she felt sorrow and a loss of a good mate, just because she she has a new horse does not mean she did not care for him.
If you wish to point fingers at people do not care about there horses, look at the racing industry, people with no knowledge or horse sense drive there horse into the ground with work or the trainers says he can't run and they push the trainer to make him run, if that trainer does not make him run they send him to someone else.
There is neglect, it has come from people who do not know alot about horses and owning a race horse is a game, these people never see there horse usually until it is at a race, they know nothing on how to train, prepare or even look after a horse. They horse usually just breaks down and is no good to them, then they sell them for meat =(
Having said all this however, I have met some wonderful owners as well that do care for there horses and some great trainers.