Yeah it is cathedrals. and personally my first thought when I heard that line was churches and cathedrals become too focused on profit. I think he's talking about an increasingly "religious" society, "when the banks became cathedrals... and the fog became God" and its apparent hypocrisy (supporting the killing of others to aid their own cause) "priests clutched onto bibles and went out to fit their rifles."
We have to remember the time period this song was based upon. just look up violet hill :)