Sounds like it's a value-judgement free decision from manufacturers to follow the incentives from the policy as we'd predict:
way cheaper and less work to make those (now pretty popular) vehicles bigger than R&D and re-tool factories to make smaller and/or more efficient. It would need to be made more efficient to get smaller otherwise you lose power. Truck owners are comparing power (even if they dont use it, and it's sometimes just brand bragging rights) so that sounds like a worse option if you're making and selling them.