Route developments is mainly down the Airlines.
Transport access is down to Government and Transport companies
Terminal expansion is down to Abertis.
Selling the advantages of improving all of the above is down to the management 'team'.
Unfortunately, very few of us actually knows what goes on behind the scenes.
What i do know is that employees, locals and pprune'ers as well may talk some pretty good sense, and its as if the management dont want to know and thunder on with ridiculous ideas pretending that they think everyone will love what their doing.
Also I think the whole catchment area thing is not the 'major' factor some people perceive it as. As Twinaisle says, the further away the route, the further people will travel to the airport to fly the route. If people are willing to travel from South Wales and the South West to LHR,LGW,BHX for long haul routes... (a drive of between 1 1/2 - 4 hrs, why wouldnt they drive to CWL if the route was there.
There are also alot of Welsh accents you can hear when a BRS flight diverts in.
I think, (and this is my personal opinion) BRS got lucky because
A) Go were there, and thats where easyjet stayed.
and B) CO has improved BRS profile.
If CWL had a sparkly new terminal the same time as BRS and a good team to profile CWL to the world, i wonder how it would have turned out.