The main push for popularity of the .45 came in reaction to the old Assault Weapon Ban. Folks figured that if you are limited to ten round mags, might as well opt for a bigger pill. The main appeal of the 9mm was high cap mags. Taking that option away caused folks to consider the ballistic advantages of the big .45.
With the end of the AWB, the appeal of the .45 diminished. Only the real devotees of the big slug have held on to it.
