The torsional stiffness is not due to distributing load to more spokes, they all actually take it evenly due to the rim fighting the inward pull (except for spokes at the bottom). Torsional stiffness is due to the spokes being at a slight tangent angle to the flange, this makes the twisting hub try to stretch the "pulling" spokes. Radial spokes would just pivot at the hole and not undergo any stretching until the hub has twisted enough to put the spokes at an angle to the flange, thus the torsional "softnesss" of radial spoking.

As for crossing the front wheel, it could be due to styling symmetry? Bikes with radial front and crossed rear wheels do look a little odd. Could also be due to wheel-building ease by needing to stock a small number of spoke-lengths?