Coevolution drives massive increases in capability.

Each side is in dynamic equilibrium with the other.

Each side wants to get a slight edge; when they get that edge it compels the other entity to meet or exceed the edge.

Each side lifts up the other, spurs it forward.

This dynamic can accelerate itself faster and faster.

A few places you see this self-hoisting quality:

Generative Adversarial Networks (GANs)

Google Search's quality coevolving with user's expectations.

Dunbar's Social Brain hypothesis, where massive increases in intelligence were driven by each person trying to model the other person's mind better.