In this scenario the next people who will be building civilization will be the ones who right now live in secular tribes - Amazonia, Indonesia, Africa. Hunter-gatherer societies will thrive after the event of global cataclysm (if they will not be wiped out), because they have survival skills, modern "civilized" human wont be able to hunt or grow food for himself. Also any remaining civilized societies will turn totalitarian and you have great example how some minor fake shit like covid made all go nuts. Probably its better to kill all without possibility to rebuild, we had a chance, we blew it.