We've never stopped his plans. The only thing he didn't foresee turned out to be a gain.
He has been consistently written as being 2 steps ahead
Also the triad might not be a needed quest for advancing into the game, but so are Bahamut or Alexander or Omega which have several repercussions and some references in the story.
The reason Warring triad wasn't a part of MSQ was because ppl complained about unlocking stuff during ARR and so we have these disjointed stories, which while they aren't directly needed they have been reported by the devs to be the canon lore of the game
