As I remember it, "SUV" was originally deemed part of the off road &/or utility (hence the name) collection and import duties were less than for sedan/streeters.
The initial boom came in Japanese imports and US manufacturers jumped on the bandwagon.
I also note that out here in utterly non-rural Los Angeles county the vast majority of SUV's (all two wheel drive) are driven by women. I am certainly not aware of any tax break to the buyer as I grudgingly pay off a 2004 Explorer.
Must add that I made the lady buy a V-8, knowing the fuel costs, because every six I drove was a risk in freeway traffic where acceleration is often safer than breaking.
My recollection is that the sequence is that:
-- gubmint passes clean air regulations in late '60s,
-- auto manufacturers reduce percentage of pollutant in exhaust by increasing displacement, leaning mixture, screwing up the timing.
-- gas mileage goes below 10 mpg, various '70s gas crises due to politics exacerbated by pitiful mileage,
-- gubmint passes regulations to increase mileage,
-- US manufacturers can't compete in high-mileage cars, Chrysler brings out the minivan, which doesn't fall under auto mileage regulations, since it is a "truck"
-- foreign manufacturers eat their lunch in minivans,
-- US manufacturers shift to SUVs and upscale/extended cab pickups
-- foreign manufactures eat their lunch in smaller/luxury SUV models and small pickups