I'm bi and could have possibly saved someone's life had I come out sooner.
How would you have saved someone's life by coming out?
I would have made an educated guess that one of my friends was sexually abused. If I had I may have literally saved their life.
Good on you for coming out, but it's not your fault for not doing it sooner. It's very hard to finally come out, and you shouldn't blame yourself for your friends' misfortune. It already happened, so just support them instead of trying to think about a what-if.
I can't stand people being hurt and knowing I could have helped.
It's great that you feel such a strong urge to help people around you. But you were not the person who abused your friend, and what happened to them is not your fault.