Most law schools, Loyola included, grade on a mandatory curve, so half the students finish in the bottom half of their class, typically for the first time in their high-achieving lives
FYI, half of all high school graduates, graduated in the bottom half of their class.
I think the conclusion you walk away from the article is that there is a big difference in pay within the field, just like every profession and MD who is a dermatologist on the North Shore is going to make much more than a GP in Peoria. It is a host of factors, some skill and intelligence based, some market based and some just chance.
The article does provide some insight however into why so many attorneys want to be judges (better pay).