It doesn't seem particularly outrageous.
Family members sue each other all the time, in order to gain access to the insurer behind the family member. For example, if a wife is driving a car and is the at-fault driver, then the husband and children passengers would sue her in order to gain access to the CTP insurer.
As for home owners, I guess the take home lesson is make sure you have insurance and cut the pesky gumnut trees down. It's not like the aunt was creeping around in the backyard in the middle of the night trying to steal something and tripped over something. It was the main entrance to the house, and the owners knew that the stairs to the front door were constantly littered with small hard nuts which could be tripped on, without being obvious to visitors.