"The timing was the problem," he said, noting the commitments the range of New Zealand talent have.
The multi-event New Zealand Festival is spanning more than three weeks in Wellington, including the weekend of the concert at Mission Estate Winery, and there are other concerts and festivals around the country.
"One of the acts I was talking to would have had 40 people on the road, but it's not as if you can quickly pull together 40 people who weren't doing anything at the time," he said.
"If the drummer's not available you can't just go out and pull in another drummer."
"While this is a competitive industry, other promoters and the show business world generally were quite supportive," he said.
"In fact, everyone has been fantastic, the support has been fantastic. That's why we fought so hard."
"Nobody wanted this," he said in a media release announcing the 25th anniversary concert was off after an unsuccessful search for an A-List replacement for 76-year-old Rock and Roll Hall of Fame member Diamond.
"It's a no-win situation, he said.
"We were sold out and had put major investment into infrastructure for the concert, and concertgoers hadn't just bought tickets. They'd also made travel and accommodation plans."
Some outcomes were unclear, he said, having emailed eight sites in the Hawke's Bay hospitality industry cancelling bookings for about 120 rooms that would have been used by the Diamond entourage and others in the production.
Mission Estate Winery chief executive Peter Holley said the losses would "not be inconsequential", probably including costs relative to the shift in the exchange rate with US dollars.
Full refunds are being issued to each of the 20,000-plus ticketholders, a process he said "looks like it's going quite smoothly", because he hadn't heard of complaints.
Refunds generally will be issued against the card details available, but there could be problems refunding tickets that had been on-sold or purchased from non-licensed outlets.
There could also be problems where credits cards have been cancelled, but he said it is intended to follow up on those that haven't been reimbursed as the process takes its course.
The light at the end of the tunnel was that negotiations with a tour for a February 2019 concert being "well down the track of securing the main act".
With the 2018 experience behind him, including an unsuccessful nine-day battle to find a replacement at 53 days' notice, he said: "The reality is that there are no such things as contingency plans in the music industry. It's difficult enough getting acts to Hawke's Bay."
Not quite a "miracle" each time it succeeds, he said, but added: "Most of the concerts have had tours built around them, the geographic location requires them to be in town by the Friday, so it becomes a three-day activity to play one show in a busy schedule."
The Mission Estate Winery Concert set the template for vineyard concerts in New Zealand from the time opera diva Dame Kiri Te Kanawa took to the stage on the outskirts of Taradale in 1993.
Since then, there were only two year Mission Concerts had not taken place - in 2009 when Lionel Ritchie's big night was rained off, and 2015 when promoters were unable to secure a suitable act.
