How did One Nation win Secret Harbour by-election?

One Nation candidate Luke Herdegen defeated Labor's Georgia Tree in Secret Harbour, giving the party its first-ever lower house seat in the WA Legislative Assembly [1, 3]. The seat had previously been considered safe Labor territory, with a margin of about 11.5 per cent, and became vacant after minister Paul Papalia retired mid-term; One Nation had already mounted a strong local campaign that was expected to cut into Labor's margin [4]. The victory is being described as a major upset in what had been an electoral stronghold for Anthony Albanese's government, echoing a similar breakthrough One Nation made earlier this year in the federal seat of Farrer [2].