I think the idea was that they had us cornered in a way. Sure we could have let loose then and it would have been satisfying but had we it would have just played into the Monetarists hands. Even if we had taken out all the Monetarists there would have been a huge leadership vacuum and the events playing out as they had would make Raubahn look as guilty as hell of coup. The rumors that it was him behind the Sultana's death would be rife and Ul'dah would probably be facing an insurrection. If any of the Monetarists had survived, our actions would look like proof to the commoners that the Monetarists most outrageous accusations were actually true.

The Monetarists had the law on their side. We had no proof they had done anything illegal even though we new they had. Raubahn was the one ignoring the law. There is no way we could have won in that situation without crippling Ul'dah's ability to contribute against Garlemald or worse, throwing Ul'dah into a civil war.

Simply put, if we tried to fight we would lose. Maybe not in combat but in the aftershocks of our actions. We need the truth of the Monetarists actions flushed out into the open before we come down on them because we need Ul'dah's people firmly on our side in this dispute before that happens. That's truth is something we just didn't have at the time. That's why we fled. So when the time was right, when the truth comes out for all to see, then we can act and in doing so be Ul'dah's champion rather than Ul'dah's foreign conquer.

Our characters strength of arms had nothing to do with it. Frankly, it actually made our characters look bright enough to realise how serious the situation was that we couldn't just start slaughtering the Brass Blades.