the accumulation of fuels is part of the problem and is a normal part of forest growth, but climate change is the other part
in California, climate change is causing longer and hotter summers, such that the fire season is now year-round (burning season has changed over the last 20 yrs). grass, twigs, needles, and even small sawlogs are dried to moisture contents lower than that of kiln-dried lumber (c. 8%), making those fuels much more flammable
ppl dont like wildfires burning near their houses houses r just more fuel) so they suppressed all fires, allowing fuels to build up for decades on end. now, when theres a fire, it burns hot as it consumed the accumulated fuels.
theres a management practice called Defensible Space that treats the house and areas nearby to reduce the risk of fire. this assumes that the area will burn someday and that burnable fuels need to be at a minimum when that happens. its up to the homeowner to apply the practice, and many take a fatalistic approach