I don't follow the belief that Rasputin directly attacked the Traveler, there's multiple instances of it saying she never intended to leave in the first place. But i do agree that he did cause some of the destruction, which inevitably saved some rather than allowed all to die, which gave the Traveler it's last chance: Ghosts. You are right about there never being anyone harnessing Light as we do prior the Collapse, we had understanding of it, we used it in a technological sense, but we were never vessels of it like Guardians are.