There's nothing incomprehensible about it. There are plenty of reasons for it with a large high temperature contribution. Certainly it's disastrous and tragic but it's not new. In 1974-1975, almost 15% of the total area of Australia was burnt. As of 7th January, the area burnt (it will clearly increase) is less than 10% of that destroyed in the earlier conflagration.

https://www.australiasevereweather.com/fires/history.htm

'An integral part of the Australian environment' https://www.abs.gov.au/Ausstats/abs@.nsf/0/6C98BB75496A5AD1C...

https://www.drroyspencer.com/2020/01/are-australia-bushfires...