The board vetoed the 767 replacement as too costly. The reason the 767 fleet was grounded was that they were triaging maintenance so much they started to ignore bulletins and finally got caught out with a number of required items being missed. The whole reason it was so stretched is that the board would not even approve temporary replacements whilst the 767s went off for deep maintenance that required them to be sent O/S. So engineering kept them flying no matter what.
It's worth having a read of how AirNZ bungled the whole thing by being greedy when they could've had a very viable airline partnered with SQ. But the Kiwi idea of partnership is that they make all the decisions and SQ just pumps in 35% with no board positions.
BTW I had dealings with the Melbourne maintenance facility in the 90s and 2000, and not long before administration was shown the empty spaces where previously there were engines and stocks that had mysteriously disappeared across the ditch.