The root cause is an unsustainable economic model, which is like a Ponzi Scheme that requires perpetual growth to enlarge the bottom layer, and it was built upon the presumption of perpetual growth. When the population declines or just grows slowly, there's no enough in the bottom to feed the top, and the whole system is in danger of collapse. However, perpetual growth is simply impossible, the natural growth rate is known as the S curve, it goes almost flat at the beginning, then rises slowly, and turns up into a rapid climb, then slows down again, and back to flat, which is the plateau, and that's where we're at.