Always seemed to me like NOT having morals killed him, and as far as it being a shock, I recall throwing the book across the room the moment he agreed to it because it OBVIOUSLY made him as dead as he was dishonored. The one character in the entire book I actually respected and understood, and he not only sacrifices his loyalty to honor, justice, his best friend and his kingdom, but in such a blindingly STUPID way that it made me wonder whether prison had shattered his mind. He surrendered the sole (but substantial) leverage he had, which meant he had no way to force the Lannisters to honor any part of the deal. Whatever Joffrey does is irrelevant (and for all the "I based it on the Wars of the Roses" talk, juvenile kings of that era were entirely pawns of whomever managed to get themselves appointed regent, usually mothers like Cersei). The Lannisters CANNOT allow Ned to live knowing what he knows, both because they can't afford it to become common knowledge and because Ned would've spent whatever life would have remained him seeking vengeance at any cost (and, clearly, if the price is right Neds honor's as negotiable that of everyone in ASoIaF). The moment he agrees to their terms he's a dead man who can save nothing and no one, but by agreeing to them in the first place he's also dishonored; he dies for nothing, and is truly the traitor he confesses to be, just for different reasons.

Ned Stark didn't die for his principles, he died for his stupidity and weakness, but that's ASoIaF for ya. I'm glad I only read one volume; I just wish I could regain those few hours better spent otherwise.