Armchair ops and Armchair CEOs. What's clear is through all the hub consolidation, Delta has determined that it's a better business decision to deal with eating the losses when things go haywire at ATL versus operating flights through less profitable or loss-making hubs just to serve as "relievers" when things go haywire at a core hub. Hubs rely on both connecting traffic and O&D that can generate better yields. Hubs like CVG, MEM (and others that have shut down like UA and CLE and AA at STL) did not have the O&D traffic and yields to integrate with the connecting traffic and that connecting traffic could just as easily be routed through other hubs where the increased frequency and seats also benefitted the O&D market.