Usually they'll rake the egg tooth across in several places, making larger slits. Then they'll poke their noses out to breathe but stay in the egg until finished absorbing what's left of the yolk. Looks like this snake made entirely too small an opening, got stuck and asphyxiated. It's not common at all, if it's any consolation. I've never lost a snake this way but have seen babies struggle with small exits. Careful use of a razor blade can usually set things right. Sorry for your loss.