It's not paradoxical and the attitude expressed by GP that it's not "rational" is exactly the sort of thinking that leads to rationality getting a bad name.

Cooperation to the detriment of the individual in the animal world is exactly the same phenomenon in a much simpler system. That is widely and repeatedly evolved so we know for a fact that the game theory works out in a vacuum (ie without human cultural factors).

Any high trust cultural behavior is similar.