What good is the truth if it spins the quadrant into war?
From who? Would the Federation start a war over the actions of a rogue element? The Cardassians would be in no position to start a war. It was the Federation that is the wounded party here. All that would need to happen is the President denounces the extremists. And says they do not represent the Cardassians as a whole. That would make the Caredassians actually indebted to the Federation for taking the high road. Such a thing would strengthen the allaince. "One of youe own killed the President, but we will look past that and not blame you at all."
When the Typhon pact looked guilty would be a more dangerous flashpoint for war.
Though I suspect the Cardassian angle was another cop out. Next novel we will have new suspects. The Ferengi framing the Romulans framing the Cardassians framing the Tzenkethi
I don't disagree that there were other angles to play. The entire result hinged on the Castellan withholding the info about the True Way involvement. But, this is where the the new Bajoran UFP President and his assumed predisposition towards all things Cardassian comes into play. I mean, he did essentially change course, electing to make Starfleet an occupying force on Cardassia.
So, it's not entirely illogical from the Castellan's perspective to withhold that info, in the hopes that she wouldn't make matters worse. Once that domino falls, the rest are lined up ready to fall. If it's later revealed that the Castellan covered up the True Way involvement, it could rightfully be suspected that she played a role in the assassination plot. Even Garak questioned whether that was so.
So yeah, Bajoran President finds out that the assassin was a Cardassian, and the Castellan covered it up... I could see Starfleet's mission on Cardassia turning from a relief mission, to an occupation. Then you've got ultra-nationalists winning the next election. Probably an insurrection. And suddenly the UFP is involved in a war it never had to be in.
Oh, and yeah, I think the True Way bit is another red herring.