New Zealanders are a flawed people. There first mistake is finding any utility in democracy. Despite that, they have the good sense to see value in retaining the MMP voting system. The appeal of this system is that it gives new, emerging parties a greater chance of being elected, and finding representation....if that is a good thing. It is good in one respect - it offers the prospect of greater competition. The contemporary two-party system is not competitive....least of all when politicians are getting a lifetime pension. There is considerable incentive for the parties to preserve this entrenched system, so expect the major parties to form coalitions in order to retain their 'relevance'.
Clearly the problems in the ACT Party did not change their view of the MMP.