The only incident that I can recall that may have weakened the side wall was that back in 2008, I ran over a piece of metal at a construction site on the highway and that blew out a inside dually sidewall right between the two tires.
If this tire that just blew was the outside dually, MAYBE the piece of metal weakened the sidewall. But 5 years later, it seems like a stretch.
At this point, we only have conjecture and this set of tires was destined for the graveyard this winter anyway.
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
'17 Winnebago View 24V, '02 R-Vision B+
RVing for 20 years & 200,000+ miles