The limiting factor contributing to the total amount of fire is the growth of trees. Naturally it'll happen due to lightning. If that's less often than human triggers, the fires will be bigger.

That's actually not necessarily the case. By creating more fires evolutionary pressure favored plants that were designed to burn, grow fast, and leave competitive seeds.

BTW much of what burns in CA is not large trees but chapparal.

The linked articles I included have more detail.

I agree that makes sense over the long term (100+ years), assuming that natural triggers are less frequent than fires put out by people.

Please read the linked articles in my parent comment.

They are natural, because humans are natural. California's vegetation has evolved to burn and quickly regrow and easily burn again due to anthropogenic fire for thousands of years.

If it were not for human involvement CA might have more fire resistant species.