The Kiwis politely declined the offer to field a BBL team from 2028, preferring their own T20 domestic series.
"I certainly wasn't surprised," Cricket Australia's chief executive Todd Greenberg told reporters on Monday.
"We've had a couple of conversations. We wanted to make sure they knew that they were welcome to join and there was an opportunity for them to do so.
"But clearly they decided to go in another direction. That's completely on them, history will be the judge."
Greenberg said while CA considers private ownership of franchises, the BBL will continue with a growth mindset.
"Expansion is really important because it shows ambition, it shows a level of ambition about growth," he said.
"And I don't think we'll be short of opportunities for expansion.
"It felt like New Zealand were a pretty natural fit ... it's a decision for them, it was probably the one that was coming."
CA has tabled a proposal for private BBL ownership, with a decision expected mid-April.
"We haven't really thought too much about what's happening in New Zealand, we're really focused on ourselves," Greenberg said.
"I mean, 15 years of the Big Bash has shown enormous growth, I think we've got an amazing product, it's highly profitable.
"And the decision that rests on Australian cricket is what we do next, so it's a (big) decision."
New Zealand Cricket announced it would pursue a proposed NZ20 franchise league for its domestic T20 hit.
The NZC board debated whether to join the BBL and WBBL, before giving in-principle support for a new league, though it stressed it wasn't a final commitment.
"There was extensive discussion on the merits of these (BBL) proposals," NZC chair Diana Puketapu-Lyndon said.
"But the board concluded that now is the right time to revitalise our 21-year-old Super Smash competition."
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