I think WW2 is just a passing episode in this development, as different countries fared differently in the war but this long-standing development has ended in r

I think WW2 is just a passing episode in this development, as different countries fared differently in the war but this long-standing development has ended in rather similar outcomes. Overall, it's that the secular society picked up from the administration structures and practices built by (mostly Protestant) churches. WW2 guilt did not stop Austria from applying this law for collecting church dues (for the Catholic church) after WW2, even if the practice was in fact brought to statute books by Adolf Hitler in 1939.