The process of colonization of the Earth by the human species consists of creating new man-made ecosystems based on the available energy and resources. These new man-made ecosystems are subsequently filled with the new people. The real reason for exponential growth in the resource depletion is the fact that we not only create new man-made ecosystems, but also need to operate and maintain the man-made ecosystems that were built previously.
The fossil fuel era allowed the mankind to add new man-made ecosystems in a very fast pace. As we reach the limits, the Seneca cliff is inevitable, as these man-made ecosystems will crash more or less simultaneously. Not due to the lack of resources, but due to the lack of energy, as the energy allows us not just mining new ores, but also rebuilding the existing man-mad ecosystems using reprocessed resources.
The rising debt allowed us not only building new man-made ecosystems, but also rebuilding the existing ones. The mortgage crisis that peaked in 2008 was not mainly about the too hight debt regarding the houses itself. As we started to use more expensive energy, it was still quite easy to build new houses using new long-term debt.
The crucial is the fact that THE ENERGY FOR OPERATING these MAN-MADE ECOSYSTEMS MUST BE CHEAP. That is why the houses were built faster than it was possible to fill them with new people: we started to experience the lack of cheap energy that would allow the people to use these houses, i.e. to be able simultaneously repay the debt and secure everyday operation costs of their lives in such new dwellings and environments. While the mortgage, i. e. a one-time long term debt, can allow one-time use of costly energy for building a life-long dwelling, the debt for everyday expenses can not rise constatly with higher energy costs.
That is why we come to the point when the prices of oil, and of energy in general, crash. We also do not need new resources for new man-made ecosystems, as it proved that the system reaches its limits, the building of new houses with high energy costs is uneconomical. So the prices of commodities go down, too.
What we experience now are the limits of the expansion of the mankind: we are not able to build and operate new man-made ecosystems and fill them with new people, as we lack the cheap energy for operating these man-made ecosystems. The rising debt brought us new amounts of unconventional oil, but we do not need this costly oil, as we do not need building new man-made ecosystems using long-term debt.
What we really need is the cheap oil for the operation of already existing man-made ecosystems.