It was used, so I don't see how the manufacturer really matters. I would be surprised if it was a manufacturing defect. It could just as easily be new owners that weren't familiar with the systems or the neglect from the previous owner. Top of the list for my Class C when I bought it was smoke detector, propane detector, and fire extinquisher (3 fire extinquishers, actually) It's currently getting a little remodeling, but I plan to change to a 12v smoke detector and adding a CO detector as well.
Having barbequed a pickup in my driveway (leaky fuel line), I've seen first hand how quickly a car can go up. And it didn't even have any plywood to burn.