Although Eucalyptus can spontaneously combust, often there can be a human agency behind it. The same thing happens here in California, as in my homeland. We have a trial currently of an accused arsonist from last year's fires. There are some odd people in the world.
They have two suspects in custody already in Victoria. As Australia no longer has the death penalty, if found guilty it is a lifetime sentence. No 'parole', never released.

My sweet mother used to say such people "should be shot," My granny would quickly add; " and then hung", much to our amusement...