Toyota RAV4 overtakes the Ford F-150 as the best selling in the US.

Yeah - but you git to live in the PNW.
(at least you're in WESTERN Washington.....)

 

The compact truck has the same standards as that F150, which has the same standards as my Outback and your Prius.

"This standard applies to passenger cars, multipurpose passenger vehicles, trucks designed to carry at least one person, and buses."
https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571/subpart-B/section-571.208

That's the vehicle code section covering occupant crash protection. The loop holes that allowed trucks to have less safety features than cars have been closed up. This is why the OG Ranger got cancelled, and Ford didn't see making a new full frame platform for that size truck worth the investment.

A full frame has its advantages. For a small truck, those advantages aren't important enough to buyers to justify the R&D costs for a platform.

This is an issue for the entire car market, not just the trucks.

But when the OG Ranger was gone, people wanting something for hauling and towing moved to a midsize or bigger truck.. The rest switched to a compact car. The auto parts store did the latter when replacing their OG Rangers.

Scroll down at that link, and you will find a formula for target mpg with a footprint factor in it. A model's target depends on its size, and it works out smaller cars and trucks have a higher target to reach than larger. A small truck can have a better mpg than a larger model yet end up penalizing the manufacture on CAFE.

Luckily someone did the math showing this.

A small truck is going to need to do around 50% better than the full size one in fuel economy in order to reduce the fleet value for CAFE. With the same basic body shape, that isn't easy.

It isn't a question of technical feasibility but of financial. The company needs to think there will be enough sales of a platform to make financing the development worth it.

The platform cost issue is a global one. The platform used for the Ranger is their smallest full frame truck one. Maybe it could be adapted for smaller, but it seems with how people globally use trucks, that the unibody car platforms are good enough.