This has all possibly changed, or maybe not applicable to USA law.....Scheduled Public Transport journeys were (are? ) legally obliged to transport all passengers booked.
Hence, you get the bribery to mitigate overbooking, by "bumping" The alternative is to lay-on a second transport to meet that commitment.
Empty Flights? Empty buses/ trains? The contract says they have to provide the service, so they do.
In the case of overbook, where, unlike trains, every Pax is assigned a seat, the cheapest way out is persuade surplus Pax to wait for the next transport.
In this case, it seems staff tried to lowball the bids, then allowed their egos/arrogance/complacency to override common-sense.
Several reports/comments on the Dark-side, the displaced man found his way back on the aircraft and seemed disorientated and "not himself"
Well! knock me down with a feather! None of the rocket-scientists involved in this debacle ever heard of concussion? Apparently the Video footage shows quite clearly that his head made a "firm" contact with an armrest, resulting in bleeding and visible injury.
They had a choice...Pay-off the surplus Pax. (too tight / stupid to organise that) OR lay on a second plane (I did hear rumour of a Viscount -size airliner flying a schedule for a single pax)
Hopefully, the fallout will refocus United's Board on ensuring they have MANAGERS
who will apply common-sense and economic prudence to the job in hand.
Meanwhile, I forsee a mass-reprogramming of these mindless droids charged with the safe conduct of the business. I also see this becoming a classic case-study in business-management training........As mentioned elsewhere, Gerald Ratner! Well done ,United, you bypassed that elementary lesson!
edited to correct fat-finger spoolung as copied by Kanga, in later quote