This article seemed like a good explaination to me..
Paradise, California had long prepared for wildfires, but only in its worst nightmares did it imagine the kind of “megafire” that last week destroyed most of the town and is becoming a common occurrence in the state.
Born of tinder-dry conditions and erratic winds, the "Camp Fire" was the latest California megafire, a huge blaze that burns more intensely and quickly than anything the state has experienced before.
The US Forest Service defines a megafire as a single blaze that burns more than 40,000 hectares.
In recent years, authorities in California have reported an increase in such large, explosive and swiftly spreading wildfires during an almost year-round fire season.
Four out of the five largest fires in Californian history have occurred in the past six years.
Paradise had not seen significant rain for 211 days, and the town, on a ridge in the foothills of the Sierra Nevada mountains, was surrounded by a potential bonfire of dry or dead trees following a five-year drought that ended last year.
Less rain and longer droughts are the major cause of the blazes, according to recent research by the US Forest Service and the University of Montana.
So too are forests choked with undergrowth, small trees and other fuel after decades of fighting fires in areas where they used to occur naturally, according to former US Forest Service officials and experts.
“Our forests are really overgrown because of poor management across the west and that is largely because of, ironically, putting out too many fires,” said Michael Kodas, author of the book Megafire – The Race to Extinguish a Deadly Epidemic of Flame. “For a century, we’ve had a zero tolerance towards wildfires.”….
https://www.thenational.ae/world/the-americas/deadly-megafires-the-new-normal-in-california-1.791540#>>3923394