Like mentioned in the article, often times the material is very obviously suspicious and banks probably know this and still turn a blind eye to it because these borrowers are low risk and much less sensitive to the high/rising interest rates of today...
Eventually this behavior goes overboard and everything crashes. In the meantime, law-abiding people are screwed by the bubble. Then they are made to pay for the clean up.
Fraud is costly, and rationalizing it contributes to the problem.