You think that at no time in the last 1000+ years there was a time when brush built up to the levels seen today?
Humans started fighting wildfires, and for decades we were pretty successful. That resulted in more fuel buildup then happened historically.
When those fire finally burn, they often burn hot enough to destroy trees that used to survive the fires.
I don’t know what the fuel levels were in this area specifically, but yes, it seems plausible that the brush might not have built up to today’s levels before.
I wonder what the quantifiable overall effect is.