Back in the day (I forget when) Peters was ousted from the National party for being a disruptor. His NZF party has, kind of, kept that disruption going within parliament and within a coalition.
Peters is a politician with enormous experience and talent... especially compare with the chumps that keep being promoted to leader of the National party. Unfortunately NZF's voter base are racist-as-shit old people. That base is reflected in NZF policy. While they have a valuable destabilizing effect in parliament and coalition, their policy is appallingly regressive.