I thought it was by the layers upon layers of interconnected unregulated derivatives valued at a few orders of magnitude above the underlying subprime mortgages given to anyone with a pulse.

I think the GP is trying to say that oil prices where the nudge that pushed the bad loans and derivatives out of stability.

I don't remember oil getting expensive back then, but it's a long time ago.

There were many involved factors, but the 2008 financial crisis was started when Ben Bernanke raised interest rates.

Now the subprime credit of entire cities is being sold bank to bank. I'd argue that's a direct escalation of the 2008 credit crisis.

That was the structural problem.

But it was swept under the rug, it was hidden by market constantly going up.

Ponzi schemes can hide in a market going up, because nobody is trying to pull money back out.

Suddenly everyone wanting their money, and the shortfall suddenly become apparent.

Oil prices suddenly made everyone try to pull money out, and 'woops there is nothing here'.