Also, Chinese build solid DC buildings out of containers. It's indeed possible.
Which providers were you looking at? IIRC Huawei was the only company providing ISO container DCs, but the were super low density (e.g. 50kW total) compared to what the original Google/Sun/HP designs were.
Shipping containers are better against fire than wood. But here it's what was inside that seems to have been a problem, not the outer structure.
How are they better? Metal structures last minutes not hours when enough heat is involved...
Just for the record so people don't get the wrong idea, SBG2 was not built out of shipping containers. OVH has other DCs that are, though.