*Yawn*
This is all quite simple, really.
In short, powerlifters have more efficient nervous systems, greater tendon strength, etc. They also completely ignore all hypertrophy except for Type IIB myofibrillar, simply because other hypertrophies add non-fuctional mass. Bodybuilders try to maximize the various way a muscle can grow, Type I, and II contractile and non-contractile hypertrophies, which in the end equates to less pound for pound strength, but a greater muscle mass.