Tuned into PPrune hoping to find some escape from the news of emotional and self-serving, irrational out-pourings from a certain individual only to find the same sentiments awash but applied to an airport!
For whatever reason Wizz have pulled out, they have - and gone. If Cardiff was making them pots of money, they're most unlikely to have taken that step. Airlines don't tend to pull out of markets which are profitable.
Cardiff has no entitlement to a greater Belfast service than it currently has, unless demand warrants growth from the present levels and the airlines (whether that be Ryanair or Emerald/EIR) believe it will be profitable to increase flights. Same for Edinburgh. The "glory days" of multiple daily services on these routes were rapidly followed by Flybe going bust. Flybe was already reducing its presence at Cardiff before it failed completely. If even Flybe in its moribund state had concluded that Cardiff wasn't working, doesn't that tell you something?
If you were Jet2 (which I'm not, btw) and firmly established at Bristol, you'd take every opportunity to grow at Bristol and maximise presence and economies of scale with the crew base, engineering, ground handling there. It doesn't matter whether you talk about Exeter, Cardiff or anywhere else - why on earth would you want the complexity of another base nearby when a sizeable number of those customers will fly from Bristol?
For them, TUI and easyJet, you also have night movement constraints at Bristol. If there are spare night slots, you take them so your competitors can't. If you have night slots, you don't give them up, otherwise your competitors take them and increase the services they offer in competition to you, denting your own performance.
There is a heap of wishful thinking here, and much of it is being emotionally driven on the "rebound" from the Wizz announcement. I hope the airport has rather clearer line of sight to decent prospects to rebuild, which are likely to focus around Ryanair as it's a) already in Cardiff and b) is actively looking to grow and c) has a business model which appears to mean 1 or 2 aircraft bases are practical.