I’m no suspension expert but it’s 100% related to the rear suspension.The limiting factor for tow capacity of the Bronco seems to be the rear suspension. The current Ranger with the 2.7L, 10 speed auto and tow package is rated up to 7500 lbs. The Ranger has a leaf spring rear suspension vs. a softer 5 link coil suspension on the Bronco. I plan to tow my 18 foot boat that is around 3500 lbs. loaded with trailer very short distances.
My 2001 Grand Marquis is full frame and a 11’ wheelbase with the same axel, transmission and engine as the f150. Yet my car can only tow 2000 while the f-150 can tow 8,000.
It’s not just springs and shocks. It’s the actual linkages. How the axel is attached to the car.
The bronco linkages are designed for off roading.
The crown Vic was designed for smooth floaty ride
F-150 was for hauling
I imagine if you REALLY want to tow with the bronco. You can get some stiffer springs and shocks and be just fine