Basically when the airport had that fude with Ryanair years ago they pushed them to Bristol. That was the death knell for CWL.
If that hadn't happened there is no reason why Ryanair couldn't have made CWL a 5, 6 or even 7 aircraft base by persuading people to travel in from a larger catchment area. Now they are at BRS its impossible but for a handful of services.
There are a few airports in the UK which only fit the Ryanair model.