You are right, it could have been easily avoided.
Let me explain; the ball python pictured is clearly a very young one. It's entirely possible that it was the snakes first time feeding live and it got a bad wrap on the prey. However; this is the part where being a responsible owner comes into play. There is zero reason that the owner couldn't have stepped in to save the snake. In my own feeding procedures I am always no more than a step away with feeding tongs ready to put those tongs between the feeder and my snake. If the mouse can bite the tongs go in their mouth until they're beyond the point of biting. If the snake has coiled the prey to the point where I can't get the tongs in place properly, I use my hands to maneuver the snake into a better position. This isn't ideal, but if it comes to me suffering a bite from snake or feeder or the snake releasing the prey entirely I'll still take that over allowing my snake to be destroyed (I have only had to move a snake into a better position one time, and in the process that snake readjusted its grip so my interference was no longer needed). If worse comes to worse, I know I am strong enough to pry a ball python off of the feeder. I invite you to post the entire story behind that gruesome picture, because I 100% guarantee you there was something that could have been done by the owner that was not done.