I've done some work in social sciences and HRs and while I'm not familiar with Delta's hiring practices (I work now in HR in medicine) I can say with certainty the aviation industry as a whole does not have good practices when they choose their employees. Hiring preferences are usually not scientific or objective.
Years ago when working in the airline industry itself, I remember a very young pilot was hired at a major (when the economy wasn't good). Out of thousands of applicants, the company I worked for chose her. 2 years later she is walking on the streets of a major downtown area drunk as could be, telling news crews she had to go to work. Unbelievable. My experience was these types of stories are not isolated.
When studies of whom to hire are conducted, more often than not a dartboard gives a better guess than a specific interview scheme (in the real world).
If airlines are weighing specific colleges, GPAs, etc., it's a shame. There is no real world correlation to employment success and productivity with such metrics.
At best hiring practices are usually dysfunctional social engineering marred in politics. At worst they become criminal negligence if customers end up dead.
As an airline customer I'm relieved aircraft are more automated these days.
Anyway, the point of this silly post: not many people in aviation have *earned* their positions. Most get lucky and benefit from an irrational system which doesn't put safety first.