None of us can evaluate the structural issues, if any. If there were no structural issues, my first guess would be the same as stated by notsobigjoe. The front of the camper needs to be higher than the rear throughout the process.
Second, you need to lower the jacks evenly. I recommend looking at levels when lowering or raising and also periodically check all of the jacks to be sure they are holding at least some of the load.
Finally I would be concerned about the ground. Was it really as hard as you thought? Did you use wooden squares or other supports under the legs to distribute the load and keep jacks from digging into the ground?
Anyway, I am sure you must feel sick after such an experience. I hope the damage was minor and you quickly sort out the issue.