I found that back in the mid 2000's the rule was changed on MHT tires, requiring DOT tires.
Tireman9 never did state what the tire was on? Given the condition the tire in his picture is in, I think it would be difficult to determine why it lost air. That is was in a external or internal situation that caused the loss of air pressure.
Simple fact in the particular forum is that we read about way to many Special(service) Trailer tire failure that have similar results. In my book it is a result of a product type that is just not robust enough for large trailers.
We have many testimonies that after repeated failures with cheap ST tires, people have switched to higher quality LT tires and their tire issues went away. That is real world results. People have stated the ST tires are very similar to LT tires in construction, however in actual use they do not appear to be of the same quality. Their inflated load ratings do not appear realistic. If their load ratings were 15 percent less instead of 15 more it might be a different story.
Chris