Cities become larger and larger, attracting people. One of the problems is that these people come faster than the housing they need. From this point of view Rome is a particular case having seen huge immigration waves after 1860, 1920 and 1945. Literally, there were no houses to be home to all these people and quarters not different from Indian slums or Brasilian favelas were created, with barracks, no sewage or any other services. These were in place well into the 1960s.
Most building initiatives were private, leaving room to speculation. There were many government initiatives in favour of social housing, but the inefficiency of these projects and violations of the law and lack of enforcement created paradoxical situations.