The goal of eliminating COVID there is to reduce the burden on the healthcare system during an active global pandemic. Until recently NZ had very low vaccination rates - zero COVID as a policy was closely tied to this and few (none?) of their mitigation measures will be permanent.
I'm a dual US/NZ citizen with family on both sides of the Pacific. It's almost comical how much negativity there is outside of NZ towards their COVID strategy, especially when you consider how minimal the disruption had been until this most recent outbreak.