Like any elite school, CMU is very far-ranging and international w/r/t student body; it’s fair to assume that a disproportionate amount of students traveling to Pittsburgh to interview, tour, and attend pre-college are from above-average means. I get the logic. I also (anecdotally) know at least a dozen students at my time there who were wholly unqualified to be there save for their family’s ability’s to pay their tuition in full, cash.
I have zero interest in litigating the value of diversity; if that had to be explained here then you’re too ideologically gone for either of our time spent to be useful. What I can say - and I suspect CMU agrees - is that education and opportunity is a great way to give underserved populations upward mobility, therefore minimizing outputs of family affluence and giving more opportunities to lower-income applicants will yield a higher overall impact. I’m sure they likely saw performance (and potentially even donor) differences between the two populations; it’s possible that the demonstrative interest population simply didn’t perform as well.