The buffeting its shares were receiving on the London stock market week after week, the perception that it was too dependent on a British housing market heading for serious difficulties, was gradually undermining the confidence of the big institutions that provide around 44% of its funding.
The new rule for any bank or financial institution in the world is don't be too dependent on any one source of funding - because in the stormy conditions on world markets, that funding can disappear, sending said bank crashing on to the rocks.
That's the main reason why HBOS last night agreed to be taken over by Lloyds TSB for £12bn.
There were signs of lenders to HBOS and depositors taking their cash back and putting it elsewhere.
If that had continued, well the consequences would have been unthinkable.
So the main benefit of its merger with Lloyds TSB is that the enlarged group will benefit from more diverse sources of finance - which should mean, to put it in crude terms, that the beefed-up Lloyds TSB will be less at risk of a run than either HBOS or Lloyds on their own.
It was exactly the same logic which drove Merrill Lynch, the big investment bank, into the arms of Bank of America at the weekend - because all the big investment banks, like Merrill, feel dangerously dependent on retaining the confidence of the big money managers and institutions that fund them.
And it's why Morgan Stanley - Merrill's great rival - is also looking for a partner or owner with more stable sources of funding (it's talking to America's Wachovia and others).
Even Goldman Sachs, the pre-eminent investment bank - in its recent heyday, one of the most powerful institutions in the western world - cannot be confident it can thrive and survive as an independent.
Also the recent behaviour of the US and UK governments has sent out a worrying message to the investment banks and their backers.
The authorities on both sides of the Atlantic have demonstrated that they'll do all they can to protect and preserve institutions that directly touch the lives of millions of people, retail banks such as Northern Rock and HBOS, mortgage funders such as Fannie Mae and Freddie Mac, or even an AIG, which has a huge retail presence.
But the US Treasury refused to prop up Lehman, which was allowed to collapse - and the salient fact about this investment bank is that it was not in retail banking.
The credit crunch is creating a new world order in banking and finance.
It's striking terror into the hearts of hedge funds, who can see their backers head for the hills at the mere sniff of an investment boo-boo by hedge-fund managers.
Conservative institutions, and those with simpler business models and a history of careful management of their funding sources, are the new superpowers.
It's a world in which Bank of America, JP Morgan, HSBC, Santander and even Lloyds TSB have the whip hand.
It's a world in which the Chinese state, if it co-ordinated the investments of its cash-rich institutions, could end up owning more-or-less the entire financial system of the US and the UK.
And it's a world in which even Morgan and Goldman may well have to surrender their proud independence.