First, there are several fires, it's not one big one. A video cropped up showing a fire starting at the base of an Edison transmission line tower as the start of the Eaton fire. Whether that's the cause remains to be seen. The only almost confirmed arson was the Sunset fire (Hollywood Hills).

Even then, So Cal is on a record dry streak at the moment, with something like less than a quarter inch of rain since last May. Then the Santa Ana winds came, with a vengeance (75 mph sustained winds in some areas). When these winds come, humidity drops to near zero. All it takes is a tree knocking into a boulder, setting it loose down a hill, smacking a boulder and creating a spark that ignites already dry brush. We are already in the middle of a La Nina year (little to no precipitation), though the Santa Ana winds happen all the time, caused by high pressure in the Great Basin in northern Nevada with low pressure off the coast. Not staying climate change isn't a root cause of the intensity of these factors, but So Cal has a history of all these conditions.