Many things happened along the way, but there is one point of commonality between the gradual decline of Credit Suisse and the sudden collapse of Silicon Valley Bank. Both institutions were utterly committed to putting clients’ interests first. Which is a great thing to do, until it isn’t. Like any others, client relationships can turn toxic, and when they do, members of management need to have the perception and courage to do the right thing. And they didn’t.

SVB’s devotion to Silicon Valley saw the bank grow rapidly — and left it exposed to risks building on its balance sheet. Its clients were often small companies with inexperienced managers who didn’t know much about finance, and who were funded by venture capitalists who wanted them to stay lean and grow fast. Deposits poured in — and created a problem. Stuffed with start-up money, SVB invested it heavily in bonds that lost value as interest rates picked up. A bank with a better business plan might have turned deposits away and avoided SVB’s fate, but then it wouldn’t have been SVB.

As Silicon Valley was to tech start-ups, Credit Suisse was to billionaires. The bank loved them and wanted to help make their dreams come true. They offered “the whole bank” — wealth management, corporate advice and balance sheet lending. Across the investment bank, we were all instructed that what we did was nice but that “ultra-high-net-worth individuals” were the clients who really mattered.

When you deliver the whole bank and something goes wrong, though, the whole bank is in trouble. And when a client works with lots of different teams, then every division thinks due diligence has been done by someone else. This is a big weakness, because it turns out that not all billionaires are great clients. From Lex Greensill of Greensill Capital to Bill Hwang of Archegos, Credit Suisse repeatedly put its name and franchise behind clients whom it ought to have turned away. Lawsuits and massive regulatory fines piled up. Profits evaporated. In the end, even the billionaires started to leave; you can be publicly shamed only so many times before it tarnishes the brand.

Now the bank has negotiated a backstop loan of up to $53.7 billion from the Swiss National Bank in the middle of the night. That doesn’t communicate a strong business. In the medium term, Credit Suisse might need less capital, not more — its current strategy is not very different from what an orderly rundown of the global business, with viable bits spun off, would look like. In a year’s time, there might be nothing recognizable from the company I worked for.

In the history of high-profile bank failures, it’s quite common to find that “the clients ran the bank.” Banks with this issue enjoy long periods of looking great, because they are close to extremely successful people and develop really good ways of serving them.

Then eventually, along comes the precise set of circumstances under which the great client becomes a risk, and the risk can’t be managed because the bank’s management hasn’t got the judgment or character to separate the client’s interests from its own. The collapsed Anglo Irish Bank was addicted to property developers. Iceland’s failed Kaupthing was too attached to the nation’s wannabe financiers. They all rose and fell with the client base that had made them rich.

This is why banking is a regulated industry. A profitable bank will rarely say no to a customer with whom it has a strong relationship. That’s why you need a stern-faced civil servant, on a fixed salary rather than a bonus, to remind everyone of the risks. The customer is not always right.