Never have the words "relationship banking" appeared so apt. Anglo Irish Bank's once-vaunted business model is now, after the ignominious resignation of chairman Sean FitzPatrick, more associated with the concealment of loans to directors than with 'know-your-customer' lending.

As chief executive David Drumm's departure on Friday shows, the bank knew its customers just a little too well. Lending a senior board member €87m over eight years and then revolving it on an annual basis in another financial institution is not the sort of relationship that pleases regulators, shareholders or the government.

It should surprise nobody that – finally – someone on a bank board has resigned. There were any number of reasons for FitzPatrick and Drumm to step down: a collapsing share price, rapidly mounting bad debts, the evaporation of profitable property lending in Ireland and the UK. What was surprising was that they stepped down for none of them. But the gap between objective reality and the bank's rhetoric has been growing for months now.

Anglo's swashbuckling, entrepreneurial culture – so widely admired during the boom when the bank consistently delivered double-digit profit growth – has proved to be its greatest weakness now that economic circumstances require a degree of humility which appears totally alien to FitzPatrick and Drumm.

Only three weeks ago chief executive Drumm and his senior management were dressing up truly alarming bad-debt charges – including a general provision of €500m – as "a demonstration of prudence... old-fashioned money for a rainy day". The fact that total impairments had knocked profits down by 37% on last year only "demonstrate[d] that we can carry 103 basis points (1.03%) of bad debt and still have a profit of €784m".

That kind of take-no-prisoners attitude – seen in other high-flying corporations such as Ryanair – helped power Anglo to the top of the heap in the last decade. Sean FitzPatrick nurtured a generation of smart, capable executives who delivered year after year of low-cost, high-profit returns to very, very happy shareholders. What sets Ryanair apart from other companies, however, is not just its success but its absolute frankness. Is there anyone who has any doubts about Michael O'Leary's vision and how he hopes to achieve? Is anyone at all in the dark about how Ryanair conducts its business?

A key component of entrepreneurialism is the capacity to face mistakes straight on. But Anglo's own statement on FitzPatrick's resignation transmitted only the slightest hint of contrition. The transfer of loans, it said, did not breach regulations, but was only "inappropriate in terms of transparency".

This is an organisation that promotes itself to graduates by proclaiming it has a flat management structure and believes in "open and honest communication". However, few things could be more obscure than a director shifting large loans from one lender to another to take advantage of differing financial calendars to hide the money.

There is a troubling echo in the way the bank has handled the estimated 15% shareholding by Sean Quinn. The bank has scrupulously avoided making any direct comment on the way Quinn built the shareholding through contracts for difference (CFDs) and has been absolutely silent regarding Quinn's own resignation from the chair of Quinn Insurance after it emerged he had improperly transferred funds between related companies within Quinn Group to cover stockmarket losses.

Testimony from rank-and-file employees which appears in Anglo's multimedia promotional materials characterises the bank as a can-do sort of place of tightly knit teams – "mates, not just colleagues" – where the culture accepts no excuses and everyone owns both their triumphs and errors. These ideals ring with grim irony in light of the still-unfolding scandal at the bank.

In the end it appears Anglo's "ownership culture" meant something much more mundane. The board and senior executives "owned" the bank and did what they wished with it. The relationships they managed were enclosed within a privileged circle of just-this-side-of-legal chicanery.

From this vantage, the bank's commitment to some unique kind of corporate culture – separate and more forward-looking than the familiar back-scratching so many feared was behind the Celtic Tiger – looks shallow and threadbare.