Market economies create economic cooperation. The dinner you ate required countless people from ranchers, farmers, mechanics, chemical manufacturers, steel manufacturers, automotive manufacturers, paper manufacturers, tubing manufacturers, oil manufacturers, fastener manufacturers and countless others working on intermediate factors of production. None of them deliberately and knowingly cooperated, rather prices in the market economy allowed for decentralized cooperation between people who don't even know each other. That is the power of market economies. Command economies cannot deliberately arrange cooperation at the same scale due to information being too disbursed and rapidly changing.

So you are correct that cooperation can become the dominant strategy under certain conditions; those conditions require a small population though.