The fact of the matter is that we have no idea what happened before the priomordial soup. If a grand civilization existed after that, it would surely have left some relic. Had such a civilization existed before then there is a possibility that they either accidentally or purposefully reset the earth. Maybe in a few hundred years, we'll realize that the earth is fucked again and the last of the survivors will make the sacrifice to reset the earth again so that some life might exist in the future. For all we know, the previous civilization had the scientific knowhow to ensure that a species would spawn and dominate that was at least similar to their own. Perhaps what we call pure now would have been deadly poison to them, while they thrived with what we call poison in the air. Just because we only know of carbon based lifeforms doesn't mean we didn't have argon ancestors.