Good choice on CVG. I live in cincinnati and ever since they started signing exclusivity deals with delta, service options have declined, forcing other airlines out, leaving a biggly(largely) vacant airfield.
CVG's downfall wasn't so much when Delta made it a hub, but rather when after Delta's merger with Northwest the hubs were reshuffled [1][2], and CVG lost out hard to the gain of Detroit.
In the acquisition, Delta gained Minneapolis, Detroit, and Memphis as hubs, while previously having Atlanta, CVG, and Salt Lake City. CVG was midway between Atlanta and Detroit. Detroit is closer to Europe, slightly closer to most of the big cities on the Eastern Seaboard, and slightly closer to Minneapolis, while also having a larger local market and a hub-friendly terminal design.
Now CVG's luck turns because the same geographic attributes that made it unremarkable vs. Detroit are very handy once you're no longer in the air. Kentucky is well-positioned between the populous midwest and the few crossings of the Appalachians. It's no accident that UPS operates out of Louisville and Fedex (after Memphis) out of Indianapolis, and former DHL's, and most of Amazon's contract fleet out of Clinton County just to the east. This triangle is well-connected by trucking both for destinations near or far.
It wasn't so much that as it is really the only decent choice...
Louisville International Airport (SDF, formerly Standiford Field) is practically ran by UPS and Bluegrass Airport (LEX) is too small for the kind of volume they want to put through and the runways are too short for the size of planes they want to land there (and though they've tried time and time again, they can't expand Bluegrass Airport because the land owners around and Versailles road). Memphis International (MEM) is further from the "center" so to speak and less desirable thusly, but it too is already pretty much ran by FedEx (and is currently the heaviest trafficked shipping airport in the US)...
There were talks for many many years about a central Kentucky airport on the land the Blue Grass Army Depot is on after it would have been decommissioned by the incineration of the nerve gas on site (or now, destroyed via supercritical oxygenation via water), but the army has been dragging their feet (as they wanted to just burn it, but Craig Williams and the Berea and Richmond community put our feet down and said "Hell no, honor your commitment to safely dispose of the material.")... Now it is starting to look like the Army may never actually decommission the depot as they're starting to ship more old munitions in (safer ones, like plastic explosives and not deadly poison nerve gas) to be destroyed via the Bechtel chemical disposal plant.
Kentucky is sort of the "shipping nexus" of the United States being closest to the center of the country while still having access to the I-75 interstate shipping corridor and cheap land for building warehouses on. Amazon really could not pick a better location than CVG at this time...
If my memory is good on the subject, I think it was because CVG was a much bigger Delta hub at the time that it was hard for them to turn it into a shipping hub and not disrupt passenger traffic.
Now that Delta has vastly scaled back operations at CVG... time's right.
I found a response from essentially the horse's mouth #1:
"So, there were about three candidate locations, Memphis and, as I recall, Cincinnati and Kansas City.
The Memphis airport had some old WWII hangers next to the runway that FedEx could use for the sort center, aircraft maintenance, and HQ office space. Deal done -- it was Memphis.
That's how the decision was really made."
