We're rich, we have a lot of land, and we had mass car ownership first. Cultural preferences like what Sonia Hirt calls "spatial individualism" also likely play a role.
In discussing how "evil" carbon is, you need to distinguish between the carbon cycle (recycles all carbon within about 2 years) and "fossil" carbon (which lingers in the atmosphere for centuries). The carbon concentration in the Atmosphere has been steadily increasing predictably enough that you can disclose your age with the atmospheric concentration of CO2 at the time you were born (there is error from the carbon cycle).
And yes, this rise is human-induced. The famous "hockey stick" graph has recently been revised. Learned of that from this 11 minute, 34 second Youtube video: What the Hockey Stick missed about climate change (paywalled links above are in the description).
And I think I know where that "depopulation to 1 Billion" figure came from. If you look at an article like this one, describing how many "Earth's" are needed to live at a certain standard on living: I can see how that can be interpreted the wrong way.
The North American standard of living is very wasteful: not only because capitalism over-produces cheap disposable goods, but also because North American cities prohibit mid-high density development in most of their land area.
> The pervasiveness of the [Single-family zoning] rule is one of the reasons for its destructive social impacts, which have been documented in great detail. In brief, there’s compelling evidence that single-family zoning has damaged the environment by encouraging suburban sprawl and car reliance, worsened affordability by restricting housing supply, and undermined inclusion by keeping lower-income households out of high-opportunity neighborhoods.
But if you are a Capitalist or Libertarian, you believe that free markets are always optimally efficient: and that any government intervention will lead to a worse outcome. Conveniently ignoring that no "free market" truly exists in a vacuum, free of government intervention.
So if you believe that Free Markets are infallible, and "globalists" are telling you that were need to cut back on our resource consumption, and the "globalists" are also telling you that you don't need to severely curtail your standard of living: I can see how one can mistakenly believe they are talking about forced depopulation.
And that does not even get into the possibility of using more efficient nuclear power in the future. Most current plants are incredibly inefficient. This is in part due to non-proliferation treaties all but prohibiting waste reprocessing. Because nuclear reactions are 10,000x more energetic than chemical reactions: nuclear plants can still make a profit consuming only about 1% of their fuel. That is mostly a tangent to illustrate some of the room for efficiency improvements we still have to make. Most environmentalists actually oppose nuclear power: primarily due to the long-lived waste of current plants. Even if they acknowledge that 4th generation nuclear, with waste reprocessing, can be done safely: they will argue that we don't have time to develop the technology. We can get most of the way there with renewables and energy storage.