We all know that Jack's intention was to detonate the Jughead to reset the occurrences that happened for the past 3 years of that point of time, changing the survivors' "destiny", but what if their destiny was to detonate that Hydrogen bomb? What if Jack had a purpose on the Island (as Eloise had already pointed out), and that purpose was to detonate Jughead so that Oceanic 815 could crash? What if the destiny of those who went back in time was to go back in time to do the stuff they did, most importantly causing the reset?