This was the racing off-season, so I imagine the dogs were suffering and dying just out of sight. And its funny, when the story finally broke, the townsfolk were shocked...shocked!... that such a thing could have happened. Nobody had ever wondered, apparently, where all these animals went after their four-year or thereabouts racing career came to an end.
The problem with Greyhounds is the same as with Huskies, I suppose: they're huge animals that eat a lot and need lots of room to run around in; taking them for a morning walk (through a desert, no less) would be quite a chore. In any event, as a result the town put in place an "adopt a Greyhound" program, and these days you don't hear the same kind of story.
It always seems worse when bad things happen to dogs. They are innocent, whereas people are assholes.