Although this year is particularly bad (weather is contributing but accidents and arson are probably also a big factor) bushfires are part of periodic cycle that renews the vegetation and removes accumulated dead plants.
Yes, normally fire is a revitalizing driving force for an area. In this case, however, given the massive scale of the fires, plus the decades-long issues with extreme drought and heatwaves, any regrowth is going to struggle, with an uncertain future.
And that's just talking about the plants. Animals die in fires, but they usually are replenished. However, given the enormous area burned, there will be much less room to recover. Plus, they will still have to deal with tentative regrowth on the brink from drought and heat.
The sheer scale of the fire, and it's compounding issues, means that the situation is much more complicated and dire than normal.
Although this year is particularly bad (weather is contributing but accidents and arson are probably also a big factor) bushfires are part of periodic cycle that renews the vegetation and removes accumulated dead plants.