Goldman stepped into the middle of the transaction because that's what they were paid (I think it was 15m?) to do. You're right that the buyer should have take

Goldman stepped into the middle of the transaction because that's what they were paid (I think it was 15m?) to do. You're right that the buyer should have taken a closer look at the underlying mortgages themselves, but that's the other part of the story, that the ratings agencies that everyone trusted to do that work for them were either on the take, stupid, or both.