Tree huggers way back when stopped clearing under growth which is what you are likely referring to. Huge mistake as it only upped the tinder.You can blame humans for the forests being too dense so that too many the trees stay small and burn rather than survive fire driving up the heat thus killing ever larger trees as they burn too.....driving up the heat yet again.
This is at heart a management failure.
They learned that lesson the hard way but then underfunded this important land management.
But worse still they let people build where they knew fire was going to come (or mudslides on the coast).
Nobody says no to development. Big problem.