There are lots of people with 40 - 50 MM - these people earned if from mileage schemes - CC bonus churn, manufactured spending, etc.
Maybe AA calibrated to minimize this group.

Having a high number of MM doesn't really mean anything - large CC spend, MS, churn, etc.

Even on UA - Tom Stoker is at say 25MM - and he is top. He flies alot from purchase of an unlimited travel pass. Now he doesn't earn any miles now - since his flights are now no-cost.

We had a contest with the head of AAdvantage to guest on top MMers, way back when they hosted a megado - and the top person 12 years ago was at 75MM. And lots of people in the 40MM range.