In a short term or limited disaster, like after an earthquake or hurricane, recovery is helped by the stability elsewhere in the world. But in a widespread disaster, the technology gets lost. Folks die and fail to pass it along to the little ones, or the little ones don't understand what they have been told due to their living circumstances. The group is concerned with survival, and due to this, schooling and the ability to practice what they are learning suffers. For instance, writing. Little children could be taught written language, but unless the group had paper and were able to write to each other, this lesson would not stick. Then the old teacher dies, and the ones taught teach the next generation, but they are even less motivated to learn, and eventually everyone just stops.
So, in like manner the great civilizations of China just disappeared. After a pole shift, civilization falls back to the stone ages to some degree, with fur clothing and hunting and gathering and the like in some cases. Civilization must start anew, again, or essentially does that. Perhaps there are some little places where this or that knowledge is retained, and spreads out again among other peoples gradually. The danger is where thugs or sadistic gangs that don't care about teaching and technology take charge. Where they rule, technology dies out because of this. So, technology and methods can be retained, but a gang can come in and destroy what's there, and then it is lost.
Offered by Nancy.