Too much trailer or not enough truck.
Your 7650 tow capacity was calculated considering a 150 lb driver, with no aftermarket accessories, no cargo, and no passengers.
----------------------------------------------------------------------
Simple example would be:
Truck has 1250 lb payload and 7650 lb tow capacity.
7650 lb trailer would have about 1000 lbs tongue weight
Weight distribution hitch weighs about 100 lbs
driver weighs 150 lbs
Tongue / hitch weight 1075 plus driver 150 = 1250 lbs needed from payload
---------------------------------------------------------------------
In theory, your truck could pull a 7650 lb trailer, but, as you can see in the example, any accessories, passengers, or cargo, would overload the truck.
Every pound of aftermarket accessories (bed liner, floor mats, bed cap, step bars, etc), people, pets, and cargo, takes a pound away from available payload and a pound away from tow capacity. If you put 650 lbs of people and cargo in that truck, it's max tow capacity is 7000 lbs. A trailer with UVW of 6000 lbs, is going to weigh more than 7000 lbs, when loaded for camping.
Towing at or near your max weight, can be quite unpleasant.
Here's a link to a program that will calculate a max trailer weight, using your specific payload and passenger / cargo requirements.