Like the GP said : this was a logistical problem. They needed to get 4 employees from point A to point B 300 miles away. There are several ways of tackling this challenge :
1. continue escalating their shitty voucher bribes : sooner or later someone's gonna bite
2. arrange alternate air transport for the crew : they're already in an airport, and 2 of their competitors (American, Southwest) have multiple direct flights between Chicago and Louisville each day
3. arrange ground transport : otherwise known as renting a car and driving. Not super fun, but I've had ironically had United pull that shit on me from NYC to DC - i.e. they cancelled a flight and put us on an overnight coach bus. If it's good enough for customers, it's good enough for the crew.
4. suck it up and delay whatever flight that crew was scheduled for. It sucks, but it was their mistake to overbook and this isn't a safety-critical situation.
Bottom line, there are about 951 different ways to tackle this problem and they chose the absolutely worst one out of the bunch. That kind of stupidity is legitimately impressive to behold.