This was incredibly interesting psychologically, even though I don't have any actual background in psychology. In my admittedly uneducated view, it seems there's a lot to learn here not just about tendency towards trust, analyzing risk and reward, things like that, but also about how the whole dynamic shifts when power clearly is balanced towards one person. They don't even necessarily trust Mike fully, but that doesn't matter. If they want even a shot they have to cooperate, or else Mike is sure to screw them all over (as he said he would). He might anyway, but in the meantime everybody else was cooperating better than they had without someone holding a clear advantage. I think Mike acted as a sort of justice system; screw up and you're punished. The result was everyone cooperated for that game and actually maximized profit.