Alan Greenspan the previous director of the US Federal Reserve bank (do not be seduced by the title, still a private bank owned , by other private banks) wrote a whole chapter in his book "The age of turbulence" Penguin editions 2008 , with title "The long term energy squeeze" where he describes how the increasing scarcity of oil will create (and has created) many minor and major crisis-es in the financial system. A rather recent example was the crisis of 1972, when the UK economy went almost bankrupt. At that time the price of oil, due to the Israel-Egypt war increased almost 5 times.
For the US economy this is even more clear, as the USA consumes about 25% of the planetary oil production which is more oil that what USA is producing. And USA is spending dollars to buy oil. The correlation of oil prices and US dollar currency rate relative to the rest of the currencies is negative: The higher the oil prices, the lower the value of the dollar and vice versa. Therefore increasing scarcity of oil, means increasing oil prices and thus decreasing value of the dollar. During 2007-2008 the oil prices almost doubled,from 80 to 140$ per barrel and then again dropped down to 50$ per barrel See the chart below:
As a consequence the reverse spike occurred to the dollar index which created a kind of "financial earthquake" to the banking system. In such an " earthquake" the weakest over-debt link would collapse. And the weakest over-debt link would be the debts of the smaller economic scale, in other words the household. Now the main debt of the household is the real-estate loans. Indeed the financial crisis of 2008 started with the securitized home-loans.
We conclude therefore that the crisis of 2008, occurred because of the over-debt pathogeny of the monetary system, and the trigger was a big fluctuation of the oil prices. The weakest over-debt link that collapsed was the householders real estate (securitized home-loans)