There will be finger pointing on this but it is better than everyone going to court because of a roll-over and fatality.
It seems few people even understand the difference between what the truck CAN carry and how much the rear axel CAN carry. Just because a truck GVWR is close to what the rig weighs on the scales, your problem seems to be mostly related to overloading the rear axel and a high center of gravity as well.
Like I say, load up that camper and go over a set of scales. Weigh the front axel, the rear axel and both axels and then look at the VIN tag and you will have answered your question about overloading the truck. The under-camper storage area that raises the center of gravity makes it lean on turns and being overloaded only exacerbates that problem. No wonder the bed was torn up.
Now....whose fault is that? Well....it isn't Toyota's fault. It is something to discuss with FWC, but even if they assumed some responsibility and fixed the truck...the problem remains....you ain't got "enough truck" for that camper. You put it back on the truck and you still are probably overloaded with a too-high center of gravity.
No offense....but a buyer who does not have at least a 3/4 ton truck to mount a slide-in camper on has to have that conversation with the mfger BEFORE signing the contract. Which means you need to fully understand if you don't HAVE enough truck or if the mfger is simply mounting what you ordered. In addition, the mfger has no control over how much "stuff" you carry and since the VIN tags reflect what each vehicle was ordered with, the GVWR and axle limits will vary, there isn't a "standard" for them either. If you had the truck ordered with special bumpers, or added a winch or carry 500 lbs or more of people/stuff that all adds up against what the truck can SAFELY handle.
Yes...you see guys here with 100-200 lbs over weight on the GVWR but what about the rear axle? The combination of GVWR, axle maximums, camper weight and the stuff you carry AND how much is on each axle as well as a higher center of gravity can all work against you and it seems this is what caused the problem.