Today's airline management is different from yesterday's airline management. The people in charge (like top management in most other businesses) have no real interest in "running a successful airline", their sole interest is making money, mostly for themselves. The particular enterprise is of no importance to them.
There's probably only one senior airline executive left with any true intererst in making his "airline" successful. As a result, it IS the most successful airline now flying.
The current trend began with the Lorenzo and Carl Ichan set. They can be compared to the CEO's of Enron and WorldCom (and others). This is why we are experiencing the upheaval that we see today. To run a successful airline you have to want to run a successful airline, not just a company that will make you personally wealthy, even though it implodes.
The problems of todays so-called "legacy carriers" did not begin with 9/11, they began much before when their leaders (people with an interest in developing an airtransportation system) were replaced by people whose sole interest was the production of personal wealth.
We would not have a "Microsoft" today if Bill Gate's primary interest was to get himself rich. Likewise, Herb Kellar didn't undertake the struggles of early SWA to make himself rich. That is why both men built successful enterprises that continue to be successful. Like all of us they enjoy money and the things that it provides, but money itself is not their sole purpose in life.
The run of airline executives we've had in the last 20 years were all better suited to managing a garment factory in Malaysia than running an airline.
It's a simplistic veiwpoint, but I think you get the drift.