It is the size, scale, and type. The fires are burning much hotter and more regularly than they have historically. If you are interested in more nuanced explanations LAND ON FIRE is a great book on the subject.
https://www.amazon.com/Land-Fire-Reality-Wildfire-West/dp/1604697008
That is part of it, but not the primary cause at all. Read. Learn.
https://www.amazon.com/Land-Fire-Reality-Wildfire-West/dp/1604697008
If you want nuance then Land on Fire is your book. Global warming is most definitely part of the problem. You can find references and data in the book. The current fire suppression tactics began in 1910 with the Big Burn where millions of acres burned and many fire fighters died. That event set the origins of how the US Forest Service deals with fire.
"Land on Fire explores the fascinating science behind this phenomenon and the ongoing research to find a solution. This gripping narrative details how years of fire suppression and chronic drought have combined to make the situation so dire"
https://en.wikipedia.org/wiki/Great_Fire_of_1910
https://www.amazon.com/Land-Fire-Reality-Wildfire-West/dp/1604697008
edit: added a wiki link to The Big Burn
The west has been burning for a long time. The current management system in place by the National Forest service is largely due to fires that were being fought at their origin in the early 20th century. There was the Big Burn that really set standard for controlling burns so they do not grow too great.
We also had heavy logging in the 60's and 70's and it caused mass floods as the trees were not in the soil to limit erosion - water pollution, ecological fragmentation and destruction.
I live in southwest colorado and have grown up in the four corners. The biggest thing causing fires here is heat, wind, drought and the proximity of human populations to large wilderness areas. A lot of fire mitigation is meant to save private property. People want the forest to manage itself and burn freely...until it is around the corner from their house.
Ultimately it is complex and thoughts like, "just sweep it up", are ignorant at best.
https://en.wikipedia.org/wiki/Great_Fire_of_1910
https://www.pbs.org/wgbh/americanexperience/films/burn/
A lot of reddit seems to be anti-book, too long it seems, but this one is a great read on the topic of fire in the west.
https://www.amazon.com/Land-Fire-Reality-Wildfire-West/dp/1604697008