If Nic is as all knowing as he's supposed to be, he should know that Fid was never truly broken. Bianca et al. were going to kill an innocent to unmake the sword, after Harry did the same thing Murphy did. Nic just smashed the blade. All he did was take it out of commission until such time as a new blade can be reforged, like has been done several times over with two of the three.
Basically, the miracle of faith that Butters did was getting it to work without the metal, not ununmaking it.
He may, but at the same time it isn't always clear how soon one can be put back together, if ever.. Actually Harry didn't do the same thing that Murphy did.. He didn't pretend to judge Lea, he didn't damn her, she hadn't surrendered, and I guess technically she has no soul if she is full Fae.. He did misuse the Sword, but he also didn't know the rules, so it merely didn't allow itself to be misused... So it fell out of his hands and Lea picked it up to trade at Bianca's place. Since an innocent being sacrificed with it was avoided, Am was never unmade... Murphy on the other hand knew better, sat in judgement, said, "damn you," and tried to execute a Denarian who had surrendered, HUGE NO,NO.. So the Sword broke.. No the miracle of faith was Harry tossing the hilt in the direction of Charity and Butters in hopes that even the hilt could be of use against the Denarian attack, which it was.. The irony here is at the beginning of the book and in Cold Days as well, Murphy questions Harry's lack of faith compared to her own.... Her lack of faith got it broken, his faith got it remade.
It make sense, if Harry is an idiot who has absolutely no understanding about how fae deals work, because if Butters is not truly in danger, Harry is doing all those things, risking breaking the deal, for nothing. He could just sit back and Butters won't die at all.
That very well could be what ended up happening.. Think about it, until he became a Holy Knight Butters is really nothing to Nic, but Nic knows he means something to Harry... Yeah, he could have gone ahead and killed Harry for refusing to kill Butters, but that would mess up his deal with Mab.. Nic's main goal was the contents of the vault, breaking the Sword was a bonus.. And yes, Harry is an idiot about how the Fae work a deal even if he should know better by now... He cannot hold a candle to Mab in slippery critical thinking..
Heck, even Uriel is fooled. The archangel risk his grace for nothing. Uriel could just told Michael that Nick can't kill Harry. Surely such a simple thing is no worse then bequeathing his grace entirely. In fact, Harry can tell Michael this truth, so does Butters and Bob. But all of them keep quiet, so it means all of them are ignorant.
Don't over work it, sure Nic can kill Harry, but he needed the mission run first, then he could kill him... Timing is everything, and Nic did try to kill him, Michael and his little dog too once the mission was complete.
I don't need to mention Murphy, because clearly in the eyes of some people, Murphy's judgements and words cannot be trusted.
Again, don't over work it, her judgement is sound most of the time, but in
this case it wasn't. It is truly only by the grace of TWG and lady fortuna that this bunch of idiots can defeat Nicodemous in his own game and save the day. Mab must be insane to allow a knight who is so ignorant on the mechanics of fae deals to cross wits with Nicodemous, so Mab is an idiot too.
She might be insane, for that matter she frequently points out to Harry how ignorant he is on the finer points of Fae deals.. Harry had to admit to it as well after the Sword was broken and he finally worked out how Nic set everything up and waltzed though the loop holes so the deal wasn't violated. And it was by the grace of the Almighty and an archangel that the idiots did defeat Nic..
Everyone is a fool, only Nick is clever. He knows everything. He predicted everything with near pin point accuracy. He need to tell Harry right to his face that it is all a ploy, before Harry could even begin to understand.
Nic is clever, and in the case of what happened in front of Michael's house, he enjoyed rubbing Harry's nose in it, very smug indeed. Even Harry had to admit Nic was very clever in this action.. But Nic blows it as well, oh he ended up with the Grail, but Harry made out like a bandit..
Harry's victory over Nicodemous might as well be deus ex machina.
In a way, and will continue to be until Nic is either killed or gives up his coin and noose for an attempt at sincere redemption.. Marcone and Mab's revenge many have brought him low, but he isn't out, he will return and Harry will match wits and fight him all over again.