To the civ you betrayed sure. To the others, not a whole lot. Plus if you're playing thinking any civ is trustworthy then you're just setting yourself up imo. Nobody is going to throw away their chance to win just so as to not break an agreement in the game.
Plus in this case where everybody else is supporting the actions to one degree or another it'd be pretty hard for them to fault the person actually breaking it basically at their behest.
Plus in this case where everybody else is supporting the actions to one degree or another it'd be pretty hard for them to fault the person actually breaking it basically at their behest.