No one here has mentioned turning with a load. I was running 10 ply rating tires on my trailers and the belts would separate which would cause the tire to blow a few miles later.
This would happen when I would make a sharp turn with a load. After blowing 6 or 8 tires, I finally switched to 14 ply rating tires and have not had any problems since. I also try not to make sharp turns with a load, especially on paved areas.
Symmetric rounded tire shoulders usually mean running on low air pressure and overheating. That boils out the sealants and you get what you got.
But, I'd replace the other one while you are at it. As far as easy peasy, having a flat out on the highway can be expensive & dangerous. The real cause is the flood of poorly designed and manufactured tires imported to the USA. Dimensionaly copied, but the parts, components, and mounting procedures are anybody's guess.
See if your tires can take 100 psi. If not, they are going to let you down. Major US brand design intent burst pressure is well over this amount for mounting reasons.
Considering what I have on-board my trucks, cars, and trailers, I prefer the most expensive tires I can buy because their cost/value is nothing compared to what they are holding up. I worked in the automotive industry for 40 years, The Far East tire industries have little concern for their product destinations. Round & black is their only requirements. Treadlife, durability, conicity, plysteer, impact damage, wet traction, noise, dry traction, cornering stiffness and balance are not part of their specifications.
Just FYI: There has been for several years (maybe 10 or more now) a process in place by many companies (started by John Deere) to alter the dimensional markings on all their CAD drawings. This is because of the huge industrial espionage attacks on US manufacturers. When an authorized user access the build manifest, they get the right stuff. Hackers get the wrong stuff. Then they try to build the clones. These fail, and the tooling and/or chemistry is patched up as best they can. Then their crap parts are sent here to dumbfounded buyers.
This tire looked just fine when starting out that morning but by the time the trailer was parked you can see it was not so fine. Funny thing is it never lost a bit of air until it was parked for the night and found it flat the next day. It was a Goodyear tire and it was NOT overloaded, just that its time was up I guess.