Climate change has led to longer, hotter summers and shorter, drier winters across the American West. There is far less snow and rain. This extended drought makes forests extremely dry, leading fires to burn more intensely and devour vastly larger areas.
Another issue is that in the 1970s, there was a move to end controlled burns in Federal forests, and to put out all fires. This means there’s a lot more fuel around to burn.
Fires now burn hotter, longer. On average, they burn more than 8x the land area than in past years.