In A6A6I5, (around there), John jumps through time strands to prevent some incidents and help out their future selves by Terezi's instructions… I'm wondering how then, if Gamzee was captured by Terezi before he went on his murderous rampage, how come in the future, all of the trolls who died because of him that night are still dead in the new timeline?

He was captured after his murderspree