Pee,
As part of the "business model" FR has to be able to twist the arm of regional airports to breaking point. They establish a route with lots of marketing support, then turn around after a short time when the local economy is doing well from it and demand double or triple the money to continue. If a regional airport fights back and refuses to bow to the bully boy tactics and extortion, FR pull out. If they didn't then they would lose the nuclear option to threaten the airports with. This sometimes means that FR cut off their nose to spite their face like in the case you mentioned.