When easy money pushed by a deep pocketed government comes into contact with the profit motive of a sophisticated, amoral financial sector, a deep fault line develops.
By "deep fault line" Rajan means a place where prosperity is likely to break. In a sense he argues everybody is to blame. Wessel's article contains much more for your consideration .
I think Rajan's argument understates the responsibility of our government which pressed mortgage lenders to lend to a diverse body of home buyers. In order to do so, lenders ended up making loans to many persons who were not credit worthy.