Part of the reason for the demise of sedans is that engines have gotten smaller and are mounted crosswise, so the front projection for the engine gets smaller and you evolve to a small suv, which is really a reshaped sedan. Also, the suv has a full-height or almost full-height trunk if you want to look at that way.
SUV’s are classified as small trucks, which also puts them in a different category for CAFE fuel efficiency rules.