Tire Blow-out scenario's please, single axle only

Had one blow last year on a back road running about 50mph. When it blew it sounded just like a rifle shot in the cab, followed by quite a bit of wiggle on the back end. Didn't tear up anything but the tire, and it was shredded. Tire was only a year and a half old so maybe I ran over something in the highway and didn't see it, or maybe it was a bad tire? Either way, 20 minutes later I was back on the road.