They were reciprocal torques of the same angle on each other, except, to an engineer, Saturn's torque on Jupiter was a tiny bit stronger. Saturn made the pivot around Jupiter. A multiplicity of such flyby days means a multiplicity of such reciprocal torque s. What happened is that the reciprocal torques converted a minute bit of orbital energy spin energy each flyby occasion. Saturn cranked Jupiter's spin rate, and vice versa.
Torques are what create spin, and repeated torques are what created rapid rotation.
More attention will be given to the delivery system later in the next chapter. But the acquisition of Jupiter and Saturn as new, inner planets did bring about significant changes to the Sun. Those virgin tides in the Sun's volatile plasma helped the Sun to increase its internal turbulence and a new, higher permanent level of radiation. The gaining of twin spins by Jupiter and Saturn are the second story of our 70-story skyscraper of cosmology. Gradualism never will have a logical explanation for this phenomenal set of twin spins for Jove and Saturn.