Being from CF5 here's my take on it.
In Cardiff we have a City divided by sport football and rugby.
I'm obviously football and find as soon as you go over Canton bridge into town as a Cardiff City fan there are many places you are not welcome ridiculous in your own city.
Also I think many, not all, Cardiff blues/Rugby fans hate us so won't cross the divide and so it's easier to be a plastic Manu or Liverpool fan.
We've always had a decent support from Ely and some of the older heads I know say when we were really shit Cardiff was the predominant support for the club.