Well, here's the question, I think, Chénier: can you be absolutely certain that Rynn never promised something utterly boneheaded to them, and didn't fully inform the realm of it? Because our impression of him in Luria suggests that he might do just that...
Rynn consulted Machiavel much on the issue, because Machiavel was involved in a lot of talks with a lot of people at the time.
Both said the same thing to Mendicant: We'll stay neutral in the Western war, but we expect to get Paisly back, and would not tolerate a realm there.
But Mendicant decided to promise us Paisly in exchange for peace, and then changed his mind and created a puppet there instead, because suddenly, D'Hara wasn't worthy of trust.
Just like he had suddenly decided that Barca wasn't a legitimate realm anymore. Or that suddenly the treaty of Evanburg didn't mean anything anymore. Or that suddenly, D'Hara's neutrality towards Aurvandil isn't neutrality anymore.
But clearly, the Chevaliers are the shining examples of honour. You can totally trust them to respect anything they say.
D'Hara offered very simple terms: give Paisly back, and it won't be used in the war. Mendicant first agreed, then changed his mind. D'Hara has yet to break their neutrality towards Aurvandil, they just did what they always said they would, for reasons purely of their own (claims to the region and Florence's aggravating attitude).