I disagree actually. The ground holds water, it only makes sense. It would also depend on how hot the summer is. I believe these fires are the worst ever because of the drought combined with the devil winds. Period.
I doubt the "grass" is as much a factor as the brush, the manzanita, etc.
Yeah, the ground DOES hold water, but after a summer like this, the topsoil gets all dried out to the same degree, no matter what witner was like. Where I lived, we had sandy soil with more clay as you went down two feet or more. That clay would stay damp year ‘round, but the topsoil was always bone dry in the summer. It didne’ help the grass any, that’s for sure; it always died and got cracklin’ dry by mid/late September.
You do make a great point about he manzanita, though. Brush gets a fire going, but it gets consumed so quickly that any fire that had to rely on just grass for fuel would be over and done, pretty fast. High winds would make it really hot, and thick/tall grass would make the flame front thicker, but it wouldn’t linger after the flame front had passed by; essentially you’d have the classic prarie fire scenario. It’d still be a thing to be feared, but your focus would be on the flame front, itself.
Now, you take that and add in all the high chapparal that’s characteristic of the southern Californian back country; now you’ve got fuel that gets started by the passing of the flame front, but keeps burning for quite awhile afterward. That thick, tangly vegetation may slow down the advance of a fire, but it also perpertuates the longevity of a fire.
Where I’m pretty sure you’re dead-on about the drought is in regard to the larger vegetation. Given the semi-arid climate of the region, most of that vegetation is of a type that thrives on low amounts of water, but drought conditions just make it all the more dry, and anything that dies off for lack of water just turns into standing fuel.
Depending on how much die-off there has been because of the lack of rain...that might very easily offset the reduced amount of dead grass available, especially if there were two or more dry years in a row.