Hindsight is 20/20. A private plane charter would have been significantly cheaper and no one would have been the wiser.

That is exactly it. Hindsight. In hindsight I'm sure a lot of the people involved would have made different decisions. That's easy, and it's easy for all of us to criticize what they did, given that we have the benefit of hindsight (and a distinct lack of solid information, so the usual outrage machine has taken hold).

This was a very rare event: in the majority of cases, they're able to get volunteers to take a later flight. In almost every single one of the cases where they aren't, the people involuntarily bumped leave without incident. I doubt anyone on the flight crew foresaw their chain of actions ending in violence, right up until it happened. And I think that lack of foresight is entirely reasonable and understandable.

United (as a company) did a poor job of handling the aftermath, though.

A more likely scenario of crew being out of position (or exceeding duty/travel time, and insufficient rest) would most likely result in a cancelled flight, and that would be relatively expensive for the airline.

The cost of involuntarily bumping 4 passengers ($800+ x 4) assuming no further incident, rapidly approached any benefit from not cancelling (or delaying) the morning flight. Total revenue for the regional flight would likely be less than $10,000.

Send the 4 employees in their United uniforms down to the Delta ticket counter?

Put the Flight Attendants on the Jumpseat, and put the pilots on the UPS flights that to go SDF. If they were truly "Space-Positive" must-rides, they would have had seating assignments.

Seriously, this wasn't hard.

I'm pretty sure they even have interline agreements covering this situation.

It would probably take a day to arrange, and then coat about $15,000 per flight hour. Not the quickest or most frugal option.

They're flying to Kentucky, not Tokyo. They're not using a Gulfstream G650. $5k/hr max.

If United (Or Republic Airline) flew an Embraer 170 (same as 3411) just for the crew that needed transport to Louisville, the cost would be about $5k for a round trip. The E170 costs about $2500 an hour to operate.

Stupidly, The cost of the likely lawsuits (even from lesser incidents, that didn't involve beaten passengers, just extremely annoyed passengers) often negates any cost saving for the airline.