Would we be surprised if Merlin said "You either build this, or you get no investment next season?"
I would imagine that’s exactly what has happened - Wickerman was a big investment for a park still recovering from past failures. To pump another £4-5m in without knowing (at the point of planning) if a £16m investment is going to be a success isn’t good business. Putting one of your own well known brands in makes sense to a certain extent, whether we like it or not.