Why do the cycles occur?

About the time the population from the last big crisis has just about died out, the existing population becomes susceptible all over again to another big crisis on the order of a depression and/or big war.

Think of the problem like snow falling on a mountain. Stability is an illusion. Quietly, the snow builds up until the entire mountain reaches a tipping point. Then one small thing can bring down the mountain. But note that it wasn’t that small thing that really brought down the mountain. It was all the things that came before. And once you reach a tipping point it is too late. That mountain will come down. It’s only a matter of timing.

We are now at a tipping now. With or without Trump, this mountain is coming down.