Its so sad to see him in such pain, with such a long time table and a ton of physical therapy ahead of him. Pilon fractures are nasty, people come back from them, but there's a chance he doesn't play football again, and that break impacts him for life.
Looking at the play, it looked like he was trying to do what he was coached to do, which was try to come down with his feet in bounds. The act of trying to keep his feet in bounds and make an awesome football play is what ultimately did him in. Rewatching it, it looks like he caught it in the air, realized he was just over the back line, and tried to bend his foot just a little bit to keep it in bounds.
So, people that understand the technique better than me, was this just inevitable? Should he have tried to come down on only his front foot, while keeping the back foot up? If you're the tight ends coach, how do you coach this one?