This is the OP.
The tire I had fail was on a single axle trailer.
Thus no twisting or side forces.
The tire had a lot of tread left. I will measure the tire that did not fail in a couple weeks when I get home from this trip.
The tires had never been loaded close to their load rating and I monitor the tire pressures with a TPMS. The tire that failed had not lost any pressure.
Reminder I caught this one before the tread was thrown.
Also I replaced both tires as it seams when one goes the others are not far behind.