Only increasing in size and heat of individual fires, but the total number of fires is way way down. More development, more clearing land for agriculture and to a smaller degree some amount of activism which protests against controlled burns because of CO2 emissions (like Australia). Also fewer resources in a lot of places to set regular burns. I suspect arson is way up, too, along with idiots who don't control a campfire.
I suspect encroachment, development and management or lack thereof has contributed to a lot of the change in numbers which have also only been computer-modeled past 30 years ago.
I'll work big fires like that every now and again as a part of my job. It's an odd combination of fun, danger and exhaustion. One of the people killed in a recent one (Montana?) used to work for us. I'd met her before at a training and she was really impressive.