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...
American banks learned to be much better at it after 2008. And given 2008 and the MBS balance sheets at central banks and the municipal budgets propped up by property values and national mortgage programs intended to encourage homeownership, this is by no means just a matter between the bank and its clients, even if you put aside the money laundering angle. Mortgage fraud destabilizes economies.