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Isn't that obvious? It's impossible for the asteroid to directly kill everything unless it's big enough to literally knock earth out of orbit
Everything died from second-order effects
The sad part is that there are more than enough resources to give everyone a material standard of life BETTER than the average 1950s American, AND to preserve and even increase all our current biodiversity for the next several eons or for however long we manage to maintain that, but it will never happen because we won't even begin to make that a reality