So, let's put this theoretical F1 car on the rolling road.

We wind it up until we have overcome the volumetric and combustion inefficiencies caused by the big valves/big ports/long-duration wide-overlap high-lift cams, and bingo! we've got it "on cam".
Let's plot a torque graph. Obviously crap up to roughly "on cam". Remember this is "strength" we're measuring. Now we're getting a roughly consistent combustion pressure, the stroke is constant, as are the number of cylinders. We would hope to see a flatish line on our graph, up until the point we can't breath enough air in, and combustion pressures drop off. The highest point on this graph is Torque, measured in pounds/feet or newton metres. Most tuners will be more interested in width of the flatish bit of the graph than the peak figure.

Now it's time to measure BHP on our F1 car.
We won't get any serious power til we're in the Torque band, then all hell breaks loose!
Let's Guess and say we're "on cam" at 15,000rpm.
We've got 10 cylinders of 300cc each, running at full efficiency, pushing the crank round with a leverage of whatever, at the rate of (and this is the important bit) 75,000 pulses of power per minute.
Squeeze that pedal up a bit to 16,000rpm (you'll need ear defenders), that is now 80,000 pulses per minute.
At the 18,000rpm redline we're packing 90,000 power pulses per minute!

So the higher we push our peak efficiency up the rev range, we cannot fail to make more BHP, purely because we're getting more power pulses per minute.