I think you are equating "human civilization" with "humanity". I agree that some people are likely to survive a catastrophe, but I don't think that what we think of as civilization is likely to survive a 90% or 99% population reduction.

Or as lifeformed put it elsewhere: "Destroying all civilization doesn't mean destroying all humans, but just the structures that hold society together. A runaway heating scenario may be a pretty effective way of doing that - all crops die, wars for food, nukes get used."