But the experiment compares MBA Ivy league students to the general population.

Yes, everyone looks after their own interests, but some more than others, like in this example the students above: > implement substantially more unequal earnings distributions than the average American

If you are, or consider yourself, part of the top "performers" you have a self-interest incentive to favour this because you expect to be among the "winners" and don't want to share with the "losers".

I.e., unequal earnings distribution looks better and better as you climb the social ladder because you benefit more and more. On the other hand, if you are at the bottom you may strongly support more equal distibution because that can only benefit you.

Same reasoning as to why workers unions emerged from the bottom, not the top.