That is a sad story.
Maybe the driver fell asleep at the wheel. But maybe a strong gust of a cross wind pushed the rig into the guard rail. As with most class C's, it is unlikely the rig was equipped with heavy duty front and rear stabilizer bars and a heavy duty steering stabilizer. Those upgrades might have prevented the accident.
I don't appreciate unwarranted government regulation, but I do feel the NTSB should require chassis manufactures to equip all cut-away chassis with heavy duty front & rear stabilizer bars along with a heavy duty steering stabilizer. The additional cost would be negligible, but it would make every motor home and box truck much safer, regardless of the endless variety of weight distributions, wind-catching shapes, and wheel-base to length ratios.