The Suns announced on Friday they had released Hart from his final year as the AFL club's reserves coach, allowing the former Brisbane Lions' midfielder to move south and link up with former Suns assistant Hinkley.
Suns chief executive Travis Auld said the club couldn't stand in Hart's way after he was offered the role with the Power.
"Releasing Shaun from his contract was a difficult decision and one made after considerable thought and consultation," Auld said.
"In the end, we agreed we wouldn't be allowing Shaun to develop as a person and a coach if we restricted him from accepting this role with significantly greater responsibilities.
"Also, with our structure and current personnel, it is also highly unlikely that we would be in a position to offer Shaun similar experience in the near future."
The Suns promoted Andy Lovell to the club's head of development while also appointing Josh Fraser and Aaron Rogers as development coaches at the end of the 2013 season.
Auld believes those positions should be enough to handle the club's reserves in Hart's absence.
"With Josh coming back to the club, along with Aaron Rogers, we are in a position to continue our strong preparations for the 2014 season without any impact on the playing group," Auld said.