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.
All of these entities are competing ruthlessly to extract as much value from each other as possible. When they don't compete, the ones they're competing with steal their lunch. See: supermarket monopsonies in Australia pushing food prices to unsustainably low levels, American farm megacorporations taking over from small farmers, everything open source getting sherlocked by amazon.
The discussion wasn't about market vs command economy but about capitalism vs socialism/communism.
See: Market socialism
The discussion wasn't about any economy except for the one we currently live in.