Most likely this was bad steel to begin with. I think it is often from Recycled steel. Or steel from China.
It is no different from how the steel in really old American cars would last so much longer than the steel in newer cars. The steel is already rotting from the inside out on the day it is made.
There are a plethora of Steel Alloys, manufacturers, “heats” and component manufacturers using the raw material.
Plenty of details to examine.
It’s not so clear on how to inspect carney rides except to throw up one’s hands and add a useful life termination date for a given set of hardware.