At the top of the list is tree branches hitting power-lines.
The power-lines in the area are operated by Pacific Gas and Electric, and PG&E has a very long history of short changing basic maintenance to improve the bottom line for shareholders.
This resulted in it being hit with significant fines for (quick Google) the Butte Fire (2015), the Rough and Ready fire (1994), the San Bruno gas explosion (2010), and (of course) poisoning people in Hinkley with toxic waste. (the movie Erin Brokovich was based on this)
The fires started almost simultaneously with reports of power outages around the origin points.
As the first reports came in Sunday night of numerous fires that would grow into one of the most destructive wildfire disasters in California history, emergency dispatchers in Sonoma County received multiple calls of power lines falling down and electrical transformers exploding.PG&E claims that these winds were "hurricane force", which is a lie.
In all, according to a review of emergency radio traffic by the Bay Area News Group, Sonoma County dispatchers sent out fire crews to at least 10 different locations across the county over a 90-minute period starting at 9:22 pm to respond to 911 calls and other reports of sparking wires and problems with the county’s electrical system amid high winds.
State fire officials said Tuesday that they are still investigating the cause of the blazes, which as of late Tuesday had killed 17 people and destroyed more than 2,000 homes in Sonoma, Napa and other Northern California counties.
But the reports of the power equipment failures began to turn the spotlight on PG&E, the giant San Francisco-based utility, raising questions about how well it maintained its equipment in the area and whether it adequately cut back trees from power lines to reduce fire risk — as required by state law.
PG&E and other large utilities in California have a long history of being found responsible for major wildfires because of inadequate maintenance of their power lines.
In April, the state Public Utilities Commission fined PG&E $8.3 million for failing to maintain a power line that sparked the Butte Fire in Amador County in September 2015. That fire burned for 22 days, killing two people, destroying 549 homes and charring 70,868 acres.
CalFire announced last year that it will seek to force PG&E to pay $90 million in firefighting costs. More than 1,000 lawsuits and claims are still pending against the utility.
“It was more than just a lack of maintenance. It was a complete disregard for their requirements of vegetation management in rural areas,” said Burlingame attorney Frank Pitre, who sued on behalf of the victims.
Winds were in the 45 mph range (sustained) with gusts (3-5 seconds) to 75 mph, which are not at all unusual for California.
If they hadn't been bingeing on their own seed corn to overpay senior management, PG&E would have had no problems, and the current disaster would not have happened.
These sorts of disasters will get worse with the impact of anthropogenic climate change.
California privately owned utilities in general, and PGE in particular, have a long record of neglecting maintenance, and PUC has an equally long history of being in bed with these companies.
Now might be a good time to look at making municipally owned utilities easier via the initiative petition process.
It gives cheaper rates and better run utilities.
Strike while the iron, and the forest, and a few thousand homes, are hot.