3 million years is NOT a sudden extinction. A meteor should have wiped out whatever it was going to wipe out in a century or two. The Darwinists would have it that Man as Human isn’t 3 million years old. It might be “sudden” in a geologic sense but it is not sudden enough to admit of a meteor explanation for the extinction of a whole class of animal life. That explanation is going to have to be narrowed down in time a LOT.
I think you may have missed the point about the dates. It is not saying they slowly died out over this period. Rather, the importance of the find is that there was an abundance of animals right up to the point of the Chicxulub impact and not a dwindling of the population preceding the impact.