We don't know what the operational fees and charges that were levied at FlyBe by the airport and handling agents.
It is well documented that Gatwick has high charges for smaller aircraft maybe Luton has a similar policy for aircraft that want to use the terminal. One Wizz flight probably contains more passengers than a combined daily operation of Flybe even if they operated to the IOM, Jersey and Newquay.
Luton will become an all jet operation using nothing smaller than mid sized aircraft. Maybe that is how the airport likes it.
Times move on but it is worth noting that both the IOM and Jersey were the oldest scheduled routes out of Luton.