I don't know about Denver but ATL and DFW have been extremely busy airports for at least a couple of decades, so I'm not sure why it wouldn't have been taken in

I don't know about Denver but ATL and DFW have been extremely busy airports for at least a couple of decades, so I'm not sure why it wouldn't have been taken into account. And if neither of those airports is a "mega hub" than I don't think LAX is either. They have the gate count, the passenger count, and the Delta/American hubs.