WW, you are correct.
They threatened Derry with withdrawal of services unless the runway was extended. The work was carried out, and they did indeed launch new routes to LPL, PIK, BHX, FAO and ALC. However, the most successful route to STN was chopped and changed from twice daily, to four a week, to daily again. Other routes have come and gone (BRS, EMA, LTN), and current routes often have their frequencies and timings messed around with.
I do however believe that RYR were making money at BHD. I've paid as much as £129 rtn BHD-BRS, which for a low cost airline isn't cheap. I don't have any idea of yield/profit etc made by RYR at BHD, but do know that a while back they said the only RYR base that wasn't profitable was Shannon. Whether that is still the case is anyone's guess.