Lawyer and chairman of the Pike River Families Group Committee Colin Smith answered that question at a public lecture in the University of Otago's moot court last night.
Mr Smith's nephew, Michael Monk (23), was one of 29 men killed in the mining disaster on November 19, 2010.
He said the disaster had been a "large part'' of his professional and personal life for the past six years.
A series of systemic failings by the Department of Labour and mining management contributed to the disaster, but the deregulation of the industry, and the 1992 disestablishment of the Coal Mines Inspectorate were major causes, he said.
"If the government had not deregulated and the existing legislation had remained and the [mines] inspectorate had been retained, this would not have happened.
"The mine plan would not have even been approved.''
The total disregard shown by successive governments for mining regulations based on 100 years of mining tragedies was senseless, he said.
"The lesson that needs to be learnt is when politicians don't listen, the risk they pose to industry and the people who work in it is significant.
"If they move to deregulate without listening to the people at the coal faces, tragedies can happen.''
Deregulation allowed the establishment of the Pike River Company whose senior management were predominantly Australian and South African, a factor which also contributed to the disaster, he said.
"Those managers didn't have experience in managing complex mining situations in a highly gassy mine.
"I think if there had been experienced New Zealand mine managers, it may have been different.''
The lack of accountability for the disaster prevented the Pike River families from getting any kind of resolution.
"It makes me so angry.
"I'm at times so angry that so many people could have stopped this tragedy in its tracks.''
