If you want to know why Rory McIlroy has so much power for a man standing 5’9″ and weighing all of 160 lbs, you only have to look at his down swing and impact/release to see why.
Forget all the nonsense you hear on television, the true secret of Rory’s power is the leveraging he creates both with his semi-classic pivot (heel comes up a little, but even that little gives him more hip turn than a fully planted pivot) and his down swing from the top.