I don't find it surprising at all. There is this false perception that only the Nationals (& Libs) are leaking votes to One Nation. In One Nation's early years i think that was definitely the case. But as the ALP have embraced Green style identity politics, it's pushed some of the ALP blue collar working class to One Nation.
Think of it this way. This demographic i refer is a group of people who are centre left, to left economically, but centre right, to right socially and on matters of national security, migration etc.
The silver spoon Libs look down their nose at them and denegrate them as a bunch of poor, white trailer trash, bludging welfare cheats. While the inner city left of the ALP and Greens sneer at them as a bunch of bigoted *insert*phobic, redneck bogans.
It's a group of people who feel disdained by the entire established political order.
Not only One Nation, but Jaquie Lambie looks to have gained a Senate seat in Tasmania largely on the back of this same demographic.