They talk alot about the small cars being pushed, but one of the bigger factors was the ecoboost v6, when it first came out and was advertised at as good or better mpg in a full size truck than a 4 cyl ranger, ranger sales dropped and ecoboost sales skyrocketed.
However like many things it proved to not hold up well in practice, they got great mpg in day to day driving, but often worse than an old bigblock dodge one ton when hauling or towing. Many ecoboost owners I have met who used them for work regretted getting them for trucks, because the 25-30 mpg would drop to 6-8 when they would hook up a trailer, alot I think has to do with how the turbo chargers handle load vs efficiency.
The other issue is size of course, alot of fleet guys do not want or need a large truck. Most of them want a small ranger or colorado or an e350 van, not an f150 or a silverado or a ram. Larger size in a truck is hard to maneuver when needed, especially in crowded lots, narrow driveways etc.
What I see similiar in the ranger crowd though is kinda what I see in the bronco crowd wanting a return, they want basic stuff that works. The bronco crowd wants a short wheel base 4x4 suv with a rugged suspension rather than a luxory suv with independant suspension and air ride with a flimsy awd tcase that could barely handle leaving the pavement let alone offroad.
Oh and an edit do not get me started on the transit connect, the 2012 model was a ford focus chassis they grossly overrated, and nearly everyone who bought one was trading them in at 60k miles due to being on their third transmission 4th set of ball joints second set of front rotors and second pcm.