Step 2: The government can't afford firefighters.
Step 3: Rich people use the tax money they've saved to employ private firefighters to only protect their property.
Step 4: Poor people are left to die in otherwise controllable fires.
I'm sympathetic to #1 on a general level, many (though not all) rich people have lobbied for lower taxes, and/or simply employee tax experts who can take advantage of legal ways to reduce their taxes a great deal. But in this instance at least it doesn't work, California isn't low tax. And your progression further falls apart at #2 because firefighter salaries aren't at the level of "can't afford it" even for California alone, let alone the federal government. California looks to have around a $144 billion budget for the 2018-19 period, and I see from a quick search a Fortune article indicating they had allocated a $442 million firefighting budget, total (which apparently got exhausted, and importantly does represent a sharp upward trend from the previous 5 years, in 2013 they spent $242m). But while a few hundred million more is certainly a lot of money, it's not at the level where it's killing California. And again, California isn't a low tax state anyway.
So no, I don't think you're justified here, or at least you'll need more support. There could certainly be more spent from by the public on the level of expense private firefighters represent, and it's not clear that there is any zero sum game here. And I don't think there is anything inherently wrong with multiple levels of response, at the theater and local levels. That's particularly when part of it is preventative, like creating fire perimeters on properties by cutting down and removing dangerous vegetation. That doesn't require the same skills, expense or risk as direct large fire containment but can be a big help. Finally, as with floods there are arguably private properties that the public simply shouldn't be on the hook to defend at all because they're in known very dangerous areas. If someone wishes to expend their own surplus resources on it though that's no different than any other luxury expenditure is it?
It is reasonable to debate what balance budget should have in all this, and whether the government should be doing more to invest in better infrastructure up front. For example, from what I can tell from various sources like this one [1] a few billion a year would cover a significant amount of buried HVDC distribution backbone. California apparently has around 26000 miles of high voltage primary lines, and about 240k miles of secondary. Focusing on the primary first it'd probably cost a good $35-55 billion based on what I can find, which is a lot but is the sort of project to be done over time and focusing on the most important areas (going through high vegetation risk spots) first. It'd add up over a decade or two of effort, and blackouts aren't free either. And it might at least be worth it to look into whether there are any economies of scale to be gained or standardization and improvements that can be done to bring the cost down further. Or instead, perhaps it'd be more cost effective to just abandon certain parts of the state, some towns may face the same issue as coastal ones.
But I don't think the negative reaction to private individual efforts is justified either, and unnecessarily creates bad feelings not conducive to further work.
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1: https://www.researchgate.net/figure/Indicative-capital-cost-...
Lobbying is a form of weak power by comparison.
There are more poor people than rich people so the poor people had to vote for those that lowered the taxes at the expense of the firefighting services, which in turn means that it cannot be that clear cut.