CabinCrewe
Can you quantify why you think this is an odd route? Given most other UK airports have a direct link to BCN.
Barcelona is Spain's 2nd busiest airport handling (pre covid) 52 million passengers a year, which is more than Gatwick, Rome FCO or Moscow SVO. For context Amsterdam, Frankfurt and Paris CDG carried circa 70 million
It had seen rising passenger numbers of 2.6 million year on year.