I'm totally confused about this sentence; its grammar seems crazy. Please help me to understand it. It is from a documentary film about ancient history I've watched.
Life wasn't easy for ordinary Egyptians, but order was infinitely better than disorder. We all remember the pyramids and pharaohs, but advances which were, in the long term, just as significant were being made behind humbler walls. (0:49:41.60)
source: Andrew Marr’s History of the World – Age of Survival
What are humbler walls? As I have watched the whole film, I think the meaning is:
Although pyramids and pharaohs were better developed than ordinary Egyptians, the significant advanced inventions of history were made by the ordinary Egyptians rather than by those pharaohs and pyramids.
What do you think about it?