According to Insurance Business Mag the closure is due to the park not being able to secure public liability insurance at a reasonable rate.

"Barra Fun Park owner Brent Stevenson said he spoke to many brokers, but insurers refused to offer coverage."

https://closed.barrafunpark.com

There is a petition there to help save the park from complete closure, the petition might help other businesses in a similar position as:

"In December, small business ombudsman Kate Carnell called for government intervention in the “failing” public liability insurance market after losses sustained in the 2019 Black Summer bushfires forced many insurers to either raise their premiums to unaffordable levels or to stop selling coverage to small businesses altogether." (quote from Insurance Business Mag)

Not a park I have ever been to, nor does it appear to be a park that would interest me, but that is not the point, a small park can deliver the best memories for some people, and can even be their gateway to many new parks.

EDIT:

The petition is actually a government petition and is available here:

https://www.aph.gov.au/petition_list?id=EN2326

Edited February 14, 20215 yr by troll under the coaster
added more info

Unfortunately this is the way the world is going, everyone blames the insurance companies but the the problem is also these idiots who try something they shouldn’t or fall over and scrape their knee and expect a big pay out. No common sense anymore and no ownership over ones actions. 
I know this all to well as my wife and I run events and insurance is the killer more often then not and all because someone wants $100,000 for a paper cut 

The organisation I'm involved with didn't operate last year from March till late December . Neither did most of the other organisations on our group insurance plan. But we had to pay the full amount of insurance last year, despite 20% income and visitors.

And this year, our premium has gone up dramatically , but at different rates to others on the same group plan.

Sometimes it is just the insurance companies.