I credit the CVT with at least part of it because of the extra smooth
power tranmission. The auto tranny will sometimes up or downshift when
in hill country, and I can feel the abrupt change in speed, especially
when it downshifts. I've been told that sudden changes in wheel speed
can contribute to the wheel breaking free.
The Prius, on the other hand, had very smooth transitions from coasting
downhill to powering uphill.