Car manufacturers did a lot of lobbying to class them as light trucks rather than cars so they can benefit from more lax emissions regulations. Then marketed the hell out of them as the more they sold the less they have to comply with the stricter emissions regulations for normal cars.

So as with every shit thing these days the big reason is to increase profits at any expense.

After successfully lobbying lawmakers to class these vehicles as light trucks rather than cars, binding SUVs to less stringent fuel efficiency standards, the industry set about slotting them into almost every arena of American life.

https://www.theguardian.com/us-news/2020/sep/01/suv-conquered-america-climate-change-emissions