Tire Blowout problems of the 2004 Ford E-450

I was driving my RV down the freeway when the inside dual blew out on the passenger side of the vehicle. Before the tire blew out I noticed a vibration on the passenger side of the RV. A few moments later the tire blew out and the tread came off completely leaving only the side walls. I do not remember running over any objects in the freeway and had not hit any pot holes. This tire was three years old with less than 5,000 miles on it. I had checked and verified the tire pressure before leaving and ensured that I had inflated the tires to the recommended tire pressure per the vehicles owner manual 80 psi. These tires were the definity dakota lt225/75/16 tire. The tire was replaced by pep boys as I had purchased the hazard warranty.