As well as the physical focus elements and being able to put all of your power (and weight) in the right place at the right time, there is also a huge mental component to breaking.
I have seen very high ranking, powerful people fail a simple break because their mind was elsewhere (distracted, exhausted, etc.), while other times they've easily done much more. IMO, especially on harder breaks (aforementioned speed breaks, power breaks of 10+ bricks, etc), the mental focus required is more important than the physical.
While this sort of mental focus can be trained through other drills (working weapons with partners comes to mind), it is clearly demonstrated by an individual in breaking.