I think I don't understand (1) and its implications. How the fact that in most of the branches we are going extinct implies that we are the most important couple of generations (this is how I interpret the trillion)? Our importance lies in our decisions. These decisions influence the number of branches in which people die out. If we take (1) as given, it means we weren't successful in mitigating the existential risk, leaving no place to excercise our decisions and thus importance.