They'll have overproduced it through perfectionism. It'l have sounded perfect logically, but it won't have felt right, will have a missing soul or magic, and they won't have known why. Either that or they'll have gone backwards with it and made the balance worse by overworking and losing the minds keen edge of musical instinct and made the whole thing a bit of a mess. I sound like i'm having a go at them :L they're an incredible team of studio genius' with MJ's composition at the center of it all, what more could you want, Mix 2 must sound better than mix 90 though, or that's what we'd be hearing to this day!