It's rng no one earns anything dude.... its all in luck..... I have a buddy that got the game before me has completed both raids over 100 times killing crota regularly as sword bearer on all 3 characters.... he has yet to get fate bringer gally or the crux.... I on the other hand have every exotic weapon and my stats are far from his.... I would say he earned it having over 2900 grimmiore and I only have 2525 grimmiore