The creator of the derivates knew they were risky
"debt obligation notes - the infamous structured debt products which turned out to be not much more than bundles of dodgy US mortgages re-packaged to look like they were almost risk-free."
Well, actually, I read an interview of the main guy that developed the software that was used to make credit default swap derivatives. (There were some made before that, but they were built "by hand" and not very common -- this software automated things so they could churn out as many as they wanted.)
Basically, he told the company he worked for that they were using the derivatives wrong -- they were treating a 33% default rate over 100 years as meaning about 3% per year, and figured they were just lucky that the defaults were nearly 0 while they were trading them. He flat out told them, no, the default rate will be near 0 when the economy is good, and very high (20%+) when it's bad, that they're RISKY! They told him to piss off because they were making so much money. (Eventually the first firm fired him over it. Then he worked for a SECOND company, telling them the same thing, and THEY told him to piss off as well.) Then they acted all shocked when the default rate skyrocketed on them and basically bankrupted them. Frankly, the gov't should not have bailed these jerks out, other investment firms DID analyze these properly and avoid the risks.
He did point out during the interview, he didn't come out of this with any money -- most of his pay was in stock options, and even though he knew his options were going to become absolutely worthless eventually (since they were abusing derivatives) he was not allowed to cash in his stock options for some number of years, and by then they WERE absolutely worthless.