Groover wrote:
Probably the new Ford Transit. When it was designed to replace the Econoline series the emphasis was shifted to interior comfort, convenience, fuel economy and weight carrying at the expense of the bulky and heavy frame needed for trailer pulling. For 2020 the passenger version of the van carried a maximum tow rating of 4,500lbs where the old E350 was rated for 9,900lbs.
Probably more about the use changing. With 4 door pickups becoming common and families smaller, those that used to pick a full size van for a tow vehicle have become relatively rare (30yr ago full size vans were one of the more popular choices for RVs).
That leaves the main use of vans as cargo vehicles that don't do much towing. With front wheel drive, you can lower the floor. They also push for efficiency, so the heavy duty frame that is critical for towing heavy, could be eliminated.
Drivetrain for a 6500lb van with a 3000lb load...only has to move 9500 lb.
A 6500lb van with 1000lb load pulling an 9000lb trailer has to move 16,500 lb and that takes a much more robust drive train.
I know the Dodge is FWD and even with RWD, Ford and Mercedes (I think Mercedes has a variety of drivetrains) have pretty meager tow ratings for the OP's 7500lb trailer.