I think it might be a general bias in the human psyche. When you're born, you're utterly dependent on the gods that are your parents (and extended village, to a greater or lesser extent) and this has selected for a bias in the human brain that expresses itself as "older people good, oldest people better".
I base this only on finding the trope of "precursor civilisation/society with the best tech" in literature from across the globe.
Before written text and easy access to books and knowledge, you also relied on the experience and skills of older people to learn and make your way in the world.
I base this only on finding the trope of "precursor civilisation/society with the best tech" in literature from across the globe.