So, correct me if I'm wrong, but I recall Le Chuck telling Guybrush just before he stabbed him that he was released from prison as soon as he explained to the ones keeping him that it was the only way to win Elaine's hand in an unholy matrimony. So, I don't see the click here. I mean, why would they release him for that, when they already held him responsible for the pox, as he, himself, told them? So, it's like:
Le Chuck: "Hey, pirate dudes, I know I'm responsible for this pox-thing going on and all, because I was the one that confessed in the first place, but could you please release me? You see, I intend to marry this Elaine chick, but I can't do it behind bars."
Pirates: "Woah, former demon-pirate dude, why didn't you tell us sooner?"
If i got that part of the story wrong, I apologize, but if not, would someone care to explain?