Two main reasons: mill refurbishment is too expensive; and they...

Two main reasons: mill refurbishment is too expensive; and they didn't have enough ore reserve tonnes for a long-enough mine life to justify the capex.
The gap between resource and reserve ounces tells the story. A lot of the resources are either too small and scattered, too low grade or in unmineable locations (town boundary etc) to ever be mined.
In my opinion this is not a good idea for IRC.

BUT: The MD has history in the area so he should know what he's in for.
I wish he'd stop referring to Bonnievale as a new discovery. It was a decent-sized mine when Varischetti was rescued in 1907.
https://monumentaustralia.org.au/themes/disaster/industrial/display/60312-varischetti-mine-rescue