Once you get over the shock of it all, you will understand while many upgrade to LT tires. ST tires are marginally adequate.
Downsizing is not necessarily the solution to a tire problem. The smaller rig is not immune to blow outs.
Research Goodyear G614 and Sailun S637. THese are both G rated tires with stellar reputation.
The risk of running the marginal OEM ST tires is no so much getting a blowout and being stranded on the roadside. The real issue is the collateral body damage
caused by the blowout.
Have you ever taken your toyhauler to the CAT scale.
Knowing your real weights will give you an idea of how much weight your tires are carrying. ST tires carrying close to their rated loads are more likely to blowout vs. a G or even H rated tire with more capacity. Knowing where you stand within the tire ratings is important.
Sorry for your trouble, but consider it a lesson learned. You are finding out the hard way that the OEM tires used on most RV's are not adequate and may fail in a catastrophic way. The solution is to become proactive and upgrade your tires before the nightmare happens. Many will get rid of brand new ST tires on day 1 and upgrade to a better LT tire. It is a shame the manufactures are allowed to use marginal tires.