No- it's primarily CAFE driven. (I'll address a small area of CAFE besides what a commenter said about CAFE below, which appears to be entirely correct and on-

No- it's primarily CAFE driven. (I'll address a small area of CAFE besides what a commenter said about CAFE below, which appears to be entirely correct and on-the-nose to me re footprint.) People for the most part didn't want larger trucks. They want the old smaller full size trucks. They are no longer an option. CAFE targets (among other reasons) have forced the market to switch to Aluminum from Steel, because you can achieve near equal performance, with lower mass and higher mpg. The cost is that aluminum is not as strong as steel, so you need more volume for equivalent strength. Plus the literal cost $. But the cheat code is that moment-arm is proportional to force, but also length-squared. M=P*L^2 and similar. So you can make some design elements lighter by switching steel to aluminum and making it bigger. Boxier. Bonus is the then new-ish popular idea of crush zone is practically baked in with the larger, lighter, less dense designs. Add in some addl (Steel to Al) complexity due to serviceability, flexure, and fatigue, (which require addl bumps in mass and/or length/ volume to meet design requirements), and extrapolate over the whole vehicle, and you get the size changes from roughly 2008 (cough, cough) to now.