It's funny that you point out Japanese companies as the actually worthwhile minivans. You're not pointing out the shitwagons dumped out there by Ford, Dodge and Chevy that were the bulk of the market. I remember the Astrovans being especially bad. There was a lot of stumbling around by US makers switching over to things like fuel injections and electronic controls. A lot of this left some amount of consumer dislike to particular brand names. Then when you add that SUV/Crossovers started showing up when manufacturing of cars had improved greatly these new models were more apt to be considered quality it made a big difference.

What? I’m almost 40, and my whole life it has been common knowledge that American cars are of inferior quality compared to Japanese cars.

It makes no sense to buy a GM Suburban or Ford Expedition because you think a Stellantis Pacifica is low quality. The Japanese minivans have always been there for purchase, if you wanted a quality minivan.

People have been choosing to pay extra for bigger, taller cars because they want bigger, taller cars to signal ostentatious consumption, not any other reason. I’ve heard this direct from many, many people on why they chose an SUV or pickup truck over a minivan (though they will couch it in terms like “cool” or “sleek” or whatever).