It was not the SWFs. This post from Econbrowser along with the SEC charges against Goldman Sachs for selling investments to Royal Bank of Scotland while at the same time shorting it has pretty much convinced me that the financial crisis was a result of leverage - levarage induced liquidity.
... most of the later egregious NINJA loans (no income, no job, no assets) were made by private loan aggregators. And where did they get the money? Again, much of it seems to have been borrowed. If you buy a mortgage-backed security (or collateralized debt obligation constructed from assorted MBS), you could then issue commercial paper against it to get most of your money back, essentially making the purchase self-financing. This was the idea behind the notorious off-balance sheet structured investment vehicles or conduits, which basically used money borrowed on the commercial paper market to buy various pieces of the mortgage securities created by the loan aggregators. The dollar value of outstanding asset-backed commercial paper nearly doubled between 2004 and 2007.
... If I buy a security, I can then pledge it as collateral to obtain a repo loan, again getting most of my money back and allowing the purchase to be mostly self-financing as long as I keep rolling over repos.
... To the extent that purchases of mortgages were being ultimately being funded by short-term borrowing through commercial paper or repos, the institution borrowing in this manner was essentially fulfilling the function of a bank-- borrowing short and lending long. If, as happened starting in 2007, those providing the short-run funds choose not to renew the loans, the institution would be forced to liquidate its long positions in a market where the underlying securities could only be sold at a deep loss. In other words, there would be a run on the shadow banking system.
Now, there are two aspects of the situation that began in August 2007 that one might choose to emphasize. The first perspective supposes that self-fulfilling fear itself is the key dynamic that propagates the crisis, as fire-sale prices create ever-spreading losses. When calm and rational valuation return, all will be well. The key problem, according to this perspective, is that would-be short-term lenders were hit in August 2007 with a sudden irrational lack of exuberance that ended up persisting over a year and bringing much of the world economy down with it.
The other perspective of what happened beginning in 2007 is that those Other People-- the ones who ultimately provided the Money that drove all this-- finally started to wise up.
So, no it was not the global savings glut nor global imbalances that caused the crisis. Yes, they may have been a contributing factor but by themselves it was not sufficient.
It was leveraged proprietary trading amongs banks themselves that did themselves in. Did RBS take the Abacus deal for itself or for some SWF? My guess is that it was hoping to make money for itself by buying into the deal for itself.
Another alternative reaosn for what happened in 2007 - the shorts started to gain momentum and began using their leverage to drive down the prices of the derivatives using the usual mechanism of rumors which led to perhaps one bank's (part of a larger conspiracy?) decision to suddenly decide to not roll over the repos - and we know the rest of the story.