PM, my experience was that you didn't need to be at all good at your job to rise to director level in charities (esp small ones) - you just needed to be pally with the trustees.
I know that had my directors worked in the private sector, there'd have been more checks on what their expenses said, for instance, but either the trustees didn't notice or care - and it's not their money or shareholder money - it's just taking from beneficiaries of the charity - and they were all little old ladies who were grateful for a couple of quid a week from the charity.
And it's all done with an "aren't we worthy?" air which began to turn my stomach in the worst way, especially when I was accused of not caring about the charity because I was called for jury service and felt I ought to go do it. These directors were taking considerable salaries, fraudulent expenses and making mine and my colleagues' lives miserable through a combination of ineptitude and calculated unpleasant behaviour and publicly, making out they were saints.
That's what got me - they were utterly disingenous and I saw what they were doing as theft, really - from beneficiaries who were, some of them, in grinding poverty. And, speaking to other employees of other charities, mine was in no way unique.
I would hope bigger charities were better.