SkipnessOneEcho; You pose a fair question;
The time that BA pulled out its cost base was nothing like where it is now, it wasnt at all as lean. FR was running a much with its new STN route and fares were low and the tradition of mega fares for EI and BAs cost little cartel were no longer possible. BA hadnt see this type of discounting anywhere else on short haul, well not the extent that FR did and lets remember it would have come through a hard few years, capacity growing enornously, Capital Airlines, Virgin and Ryanair had all had their fight for passenger. BA were popular but the return was marginal.
When Bmi arrived it was what everybody wanted and Aer Lingus was reputed to have been losing £6 per passenger on Dublin London Heathrow.
British Midland arrived 1988 and stole the thunder witha amazing service, 8 departures a day (6 at first) and diamond service with food served on practically every flight, BA were getting challenges on every side. ORK and SNN were axed mid season before DUB in the same year. Some services were on 73S, B11 and interestingly 757!
The last season of BA on DUB LHR they introduced a 0615 departure with BAC1-11 and to date to the best of my knowledge there never were flights leaving for London that early!!
For a time around 1991, (immediately after Gulf war) Dublin went without a link to London Gatwick for a time also