It has to do with new standards for fuel effiency being based on the size of the vehicle.

In the Obama era, Edmunds explained, fuel economy regulations “changed from just a straight average across the board to what’s called a platform-based fuel economy standard. So your fuel economy target for a given vehicle is based on its wheelbase and its tread width, which is the width between the tires left to right. So if you multiply that you find the area of that rectangle and there’s a table that shows what your fuel-economy target is. The bigger the vehicle, the smaller the target.”

In other words, the regulations put in place to get better mileage out of vehicles also led to an increase in truck size. “There was kind of an incentive to maybe stretch the wheelbase a couple of inches and set the tires maybe an inch [farther] apart, because you get a bigger platform and slightly smaller target,” said Edmunds. “Now, the bigger vehicle would be heavier and might use more fuel, so it’s not as easy as just doing that. But certainly there was a feeling that if they did need to make it bigger to accommodate more passengers, the fuel economy target wouldn’t be onerous. They could do it.”

Basically, it was easier to make bigger trucks than it was to build more efficient engines, so we have this gargantuan trucks pushed on us and then they go "ITS WHAT THE PEOPLE WANT" because there are literally no other options besides these giant trucks if you want something with a bed.

Like, even the "small trucks" like the modern Rangers and Colorados are about the same size as the 90s F150s and Silverados. Its nuts.