I guess it's important to factor in that there are a couple of material things that have likely contributed to Flybe's decision.
1. At the time they launched DUBLCY, it was to go up against a weak incumbent in WX. Only after BE launched did BA also decide to compete and lauch its own services.
2. The decision by WX to sell and lease back some of its RJ fleet has likely provided them cash to compete for longer.
On the face of it, with no change in competitive environment approaching I guess BE have decided to put their efforts elsewhere - not an unreasonable decision on the face of it. In the end, WX still have competition on the route which was the intention when BE started, it just comes from BA, not BE. Should WX fail in the future, I think it reasonable to expect BE to jump back in once more.