Caporegime
The last Australian Prime Minister to serve a full term was John Howard, who left office in 2007. Every subsequent PM has been removed from office by their own party before their first term was complete.
Today the Prime Minister was replaced yet again. Scott Morrison is our 6th PM in 11 years.
The reason we're going through Prime Ministers so quickly is that both major parties are currently torn by factional infighting. If the polls look too bad for too long, there is great pressure to change leaders before the next election to improve the chance of retaining government (our last PM lost 34 polls in a row).
It's crazy, but this is what you get when politicians lack any kind of long term vision for the country. Everything is driven by weekly polls and focus groups.