The collapse of the investment bank Lehman Brothers impacted the financial world globally, which meant that they needed a massive bailout, especially when their debt was 60 to 1, when it should be 10 to one.
Because of this crisis in the US (which was solved rather quickly), the EU market also fail, and they needed a bail out too. The problem escalated from a US problem to a world wide problem in a couple of days, causing a great recession.
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