My understanding is that the Buddha is said to have "rediscovered an ancient path" which, presumably, formed the core of his teachings.
My question is: Why was it lost to begin with?
And why is it that the teachings of the Buddha are so voluminous and contain so much redundancy?
UPDATE: I am absolutely convinced that the Buddha's 8-fold path leading to the end of suffering does so by training the mind to respond to the pain of unskillful moves caused by unskillful predictions by (1) restraining the hindrances and (2) investigating with the intent of processing the feedback for insights to improve the predictive model of the sensory-motor brain so that more skillful predictions leading to more skillful moves will be made.
Why does this lead to the end of suffering? Because although pain is inevitable, suffering is a choice. Specifically, suffering is the choice to cling to wrong views because doing so leads to the descent into the hell of uncertainty. As the world descends into chaos, those who cling to views will descend into chaos along with it because they are refusing to "see things as they actually are."
In other words, clinging to "wrong views", views which do not correspond to the evidence of sensory experience, is unskillful.
Accordingly, please offer only answers that do not violate the scientific method of inquiry. For example, claiming that a human being lived for 80,000 years without offering evidence to support this extraordinary claim is not desired.