No one is peddling the 'elders of Zion' BS here. You have great knowledge of the financial industry, you might be able to shed some light on the role of Lehman Brother's role in regards to the GFC.
Whole books have been written about the global financial crisis, but I will try to condense it down into a super executive summary, so please forgive the short-cuts I use in explaining this:
Lehman Bros was primarily a victim of the GFC, not its cause (I would blame Countrywide Financial and Washington Mutual for aggressively loaning so much money to deadbeats and liars; Deutsche Bank more for its role in the creation and popularization of the CDO structure that appeared to make packaged tranches of such junk mortgages appear to be of the highest rating; AIG for its reckless sale of CDS to insure the mortgages; and Goldman Sachs for its culture of trading against its clients to aggravate the situation).
Finance is, in a sense, a matter of faith. As a simple example for the retail banking world, when you deposit money in a bank, you expect to be able to withdraw your money at any time you choose, but generally speaking, you only withdraw a little bit at a time as needed. The bank uses this fact to engage in what is called fractional reserve lending--it keeps only approximately 10% of actual deposits on hand, and lends the rest out.
Corporate finance is similar. Banks transact with each other as counter-parties under the assumption (faith) that their counter-parties are trustworthy and will fulfill their contracts and obligations. They can gauge this trustworthiness from quarterly balance sheet statements and how the credit market is valuing their debt. But in times of severe strain, like that experienced under the GFC, such assumptions are often invalidated. In Lehman's case, it made some bad bets on the mortgage instruments it was holding, and suffered large losses. This, in turn, caused the market to lose faith in Lehman's solvency, so the credit market stopped lending money to Lehman.
I don't want to get into too much technical detail, but financial institutions borrow money from a highly liquid money market overnight to fund daily operations and provide sufficient working capital, and in normal times, this market is both highly liquid and very cheap. But because the market was already starting to panic about the mortgage market, which is the bedrock of most banks' operations, Lehman's announced losses meant that this overnight money market just instantly dried up for Lehman. Lehman just ran out of cash in a few days, essentially. And as the value of mortgages continued to crash, the asset side of its balance sheet crashed, too, until it had more liabilities than assets, and without the prospect of being able to repay its obligations in a timely manner--i.e. the definition of bankruptcy.
An important note: until hedge funds conspired with Deutsche Bank to create CDOs, it was literally impossible to short-sell mortgages. This "financial innovation" helped accelerate the crash of mortgages and created the emergency situation that confronted Wall Street; otherwise, it would have been a rather gradual cycle of asset write-downs as the various mortgage borrowers defaulted.
Since Lehman was a critical (if not central) player in the credit (debt) markets at the time, Lehman's crash more likely than not would have brought down the entire financial system. That's why when Lehman collapsed, there was that emergency weekend meeting between the Federal Reserve, the US Treasury, and Congress to try and work out a bailout package before the Asian market opened on Monday. It's also why Goldman Sachs converted (or should I say, was allowed to convert) overnight from an investment bank structure to a wholesale bank structure, so it would be able to draw emergency funds from the Federal Reserve (and thus avoid the fate of its fellow investment bank, Lehman Brothers, which did not have access to the Federal Reserve cash).
I think the rest is fairly well understood by everyone. The banks were given a bailout to protect their depositors and counter-parties. AIG, which had insured every piece of garbage that crossed its desk, was given a gigantic bailout. Central banks across the world made emergency currency swaps to prevent the sovereigns from defaulting as well. Institutional investors who had been suckered into buying garbage mortgages experienced severe pain, or were wiped out. Since the banks had been so leveraged, they were forced to liquidate their holdings at fire-sale prices, thus causing extreme distress in both the stock market and credit markets, which crashed for another 6 months until QE1 was initiated.
I can't say I understand where Zionists come into the picture. This was a failure across the board, of banks, mortgage lenders, regulators, politicians, investors, and mom and pop liars (I mean, borrowers). Whether or not they believed a Jewish homeland should be established in the area now called Israel doesn't seem to have had an impact on their ability to profit from or be destroyed by the global financial crisis. Many Jews and non-Jews profited, and many Jews and non-Jews were bankrupted in the process.
If we misdiagnose the problem ("it was the Zionists!"), we will not be able to resolve it successfully or prevent it from happening again in the future. Let's be clear eyed about the issue, which is that we need to make sufficient contingencies to deal with human failure, whether that failure is intentional or not, or malevolent or not.