You don't need to earn £50k a year to get a visa, you just need to appear to be able to support a wife in the UK financially. To the ECO it looked, on paper at least, as if he was living beyond his means, or he may even have concluded that he was in serious debt, because he appeared to be permenantly overdrawn. It's no good earning £50k a year if your spending £51k a year.
Iain.