Are you say that you have that large RV off the ground on stands for 3 months? Can you elaborate as to what was going on as that may be a clue.
What is the date code on the tire? and is it same date code or code as the other tires? Are you the original owner? How many miles on the tires?
If I go strictly by what you put in 1st post, I would want to think a failed tire repair that should not have been performed on the side wall, but you say a loud bang!!! ? So that means some sudden external force
I would have the tire inspected by a Michelin or a Goodyear facility. Same goes for all of the others, but as tires are likely 6 years old, I would be planning to replace them all assuming everything else is okay with the RV? I wouldn't buy all of the new tires to sit on stand for months in my driveway though?