Kinda Obvious, Really

I'll bet most rich people reading the article in the NY Times nod and think it doesn't apply to them, but rich people do care less.  I wonder, however, which way the cause and effect goes.  Is it that becoming rich induces people to care less or is it that people who care less are more likely to become rich?  I can see either, but the latter makes pretty good sense.  It is easier to become rich if you don't care about others.