I've lived here a very long time and I think it is a combination of things. Obviously the changing of the seasons and the long term climate cycles - late Summer and into Autumn when it's at it's driest is when Aussies are most vulnerable, but also the distribution and increases in human population into areas traditionally more vulnerable to fire. We've a lot of new housing development (SE Australia). A fire that wiped out a few thousand acres of scrubland wouldn't make much of a news worthy story but a fire that wiped out acres of new housing and killed folks does.
Also, I think it comes down to just bad luck - being in the wrong place at the wrong time.
Fires will always be with us.