Lots of the weight gain is also from a desire for better safety.
Karen wants a taller vehicle so she can see better and Chad wants a truck that makes up for his lack of girth. Oems keep needing to make Karen's car taller and stronger so that Chad's quits flattening Karen's. Now we have trucks that require a frakking ladder to get to the bed, and crossovers taller than any truck made before 1996. Then they went and made the headlights out of friggin laser beams.. Ugh.
The oems get to pump out a few EVs as compliance cars in smog cities (where they get extra credit) and maintain their CAFE standard despite a fleet of 15mpg clunkers causing the crappy air in the first place. Shell game indeed.
Mpg requirements are dumb. Let customers decide how much gas they want to buy. If we care about air, vehicle should simply have a reasonable emissions per mile limit. If an OE figures out how to burn a hundred gallons of gas and produce nothing but rainbow stew, who cares?