Centrelink and the Robodebt recovery system

Centrelink’s 'automated debt recovery system' - or Robodebt - sparked two Senate inquiries, an Ombudsman inquiry, numerous court cases and caused enormous stress to thousands of Australians. The Robodebt system has now been found to be unlawful by the Federal Court, but several questions remain unanswered. How and why was this system introduced? And why was it allowed to run for so long?