I think the context here is that New Caledonia wants to be an independent country, and has had several referendums to try and do so electorally. France is doing everything in their power to block New Caledonian independence, using both politics and violence against natives. By granting voting rights to French immigrants, it will increase France’s apparent political support on the islands and make it harder for them to achieve independence, ensuring France can continue to plunder the islands.