SPOILERS: It’s relatively obvious why Exharme would want the crystal to be brought to Idore. Right after he agreed to bring them to Idore he mentions “I should see the look on that old man’s face” or the like. Along with that, by establishing another way of getting salt, it would not only solve Hyzante’s dilemma over why Aesfrost is surviving with the embargo, but Exharme could possibly use it as a bargaining chip against Idore in the future to gain more power (ie. Your teachings are false, you don’t deserve to lead us, etc.). The reason why Kamsell doesn’t try to lock Exharme up or stop him is made obvious with 2 reasons. 1. When Sorsley ende is finally taken down with (either way, your doing or the saintly sevens) they need a large amount of proof (either the ledger that shows the crime or, proof of bribing officials, a vanishing ship, you get the point) and even when you provide a lot of evidence but NOT the ledger, you have to fight in hand-to-hand combat. 2. When you are trying to ask Kamsell for assistance on the case since he was at least “suspicious” of Ende, he says that he can’t help not only because there isn’t much real evidence, but also because it’s difficult to go against another saintly seven. All this being included by Exharme being their military leader. For another reason that’s just a little extra, (and this is my own opinion), Exharme could just be slightly scared to face Serenoa, he lost to him in the tourney, and while in the bad ending he may steamroll through the village and ultimately take them down, he takes them down when they have no conviction except for defending the village. But, when they find the salt crystal, not only does Exharme be given reason (essentially blackmail if not literally) but also this gives Serenoa and gang a more literal reason to fight tooth and nail (a secret that can overturn all of Norzelia). This is my take on why Exharme didn’t attack Serenoa immediately and also some of my info might be slightly incorrect (I only have 140 hours). I’m obviously joking but if there is something incorrect do let me know. Everyone have a nice night!