I had both rear Goodyear's on my Acura have similar failures. The outside sidewall appeared okay, the inside was crumbling. I also caught them before they blew out or failed. These were not directional tires so the construction should have been symmetrical. Hadn't been run flat or with low pressures. They just went bad. The tire guys said low profile tires run in hot weather seem more prone to it, but couldn't explain why. They were under the treadwear warranty so he pro-rated a set of replacements based on the level of tread left.

Check your other tires. If one was like this, the others may also be.