My contention is that Stobart should have been aware of that possibility and considered the impact on SEN's credibility if the DUB-SEN were to close. With time in hand they could have made plans to reinstate the route under Aer Lingus Regional branding of this core route, if I can use that word. Even if they had decided that DUB-SEN no longer featured in their plans Stobart could at least have taken steps to try to ensure it closed in an orderly fashion that did not antagonize passengers or harm the image of SEN. After all Stobart does have a partnership agreement with Flybe.
I agree that dropping of SEN-DUB is less than ideal for the airport. Airlines can't just pick up routes at the drop of a hat, however. Storable operate 11 aircraft for EIR, soon to be 12. BE taking over SENDUB released 6 rotations a day, which were then used for other routes and to launch some new ones. EIR just don't have the capacity to launch SENDUB right at the moment, unless the get more aircraft.