Why couldn't Snape and McGonagall prevent what Fudge did at the end of Goblet of Fire?

Question

In Goblet of Fire (The Parting of the Ways), Dumbledore says to Snape:

“Then go down into the grounds, find Cornelius Fudge, and bring him up to this office. He will undoubtedly want to question Crouch himself. Tell him I will be in the hospital wing in half an hours time.”

Later, in the hospital wing:

“You should never have brought it inside the castle!” yelled Professor McGonagall. “When Dumbledore finds out–” […]

Snape:

“He insisted on summoning a Dementor to accompany him into the castle. He brought it up to the office where Barty Crouch –”

And McGonagall:

“I told him that you would not agree, Dumbledore! I told him you would never allow Dementors to set foot inside the castle, but –” […] “The moment that – that thing entered the room,” she screamed, pointing at Fudge, trembling all over, “it swooped down on Crouch and – and –”

Snape and McGonagall both saw the Dementor before he came into the room, knew that Dumbledore would disapprove and knew what a Dementor could do. Both knew how to do a Patronus charm and it seems to me that at least McGonagall saw the Dementor executing the kiss. McGonagall had orders to protect Barty Crouch, she and Snape had time to talk to Fudge about the Dementor but nobody did something about it. For starters, they could have insisted on talking to Dumbledore before letting a Dementor in the school (especially since Dumbledore didn't even let Dementors in the castle when everybody thought Sirius Black was running amok in there in the third year).

So why didn't they do anything to stop it?

Answer 1

Because of the kind of power structure underlying the Wizarding World.

As Pharnabazus outlines in his amazing essay on the patron/client dynamic in Harry Potter, Dumbledore and Fudge have a complicated history of influence and struggle. While originally Fudge allied himself with Dumbledore, the Minister slowly tried to cultivate his own patronage. During the events of the Harry Potter novels Fudge found his tenuous power base threatened by the rise of Voldemort and so distanced himself from Dumbledore's camp. We see the progression much more clearly later on in the series, but the ending of GoF is a crucial turning point:

Before the end of GoF, Fudge still appears to respect Dumbledore. He enjoys the alliance of Dumbledore's power base, even if he's not part of it himself; they are a lopsided team. Fudge has great resources but little influence and a tenuous power base, while Dumbledore has enormous influence and a very wide and deep power base.

Silencing Crouch was a deliberate move to consolidate Fudge's power at the expense of Dumbledore's. If Dumbledore used Crouch to prove Voldemort's return, Fudge's promises of normalcy would crumble and his clients would flock to Dumbledore. On the other hand, if Dumbledore were made to look like a paranoid old man...

So while it was appalling to watch, Dumbledore's clients were politically unable to stop Fudge without Dumbledore's explicit authorization --regardless of their magical or physical ability to do so-- because Fudge was a valuable ally of Dumbledore. When Dumbledore removed his support from Fudge because of this action, it is a visible blow to the Minister (who as of CoS had been running to Dumbledore for advice regularly) and goes a long way to explain his apparently irrational behavior in the following years.

Answer 2

Neither McGonagall or Snape had any reason to expect that the dementor was actually going to kiss Crouch. Their objections to the dementor had nothing to do with Crouch per se; they were simply objecting to the very idea of allowing a dementor into the castle, something which Dumbledore was adamantly opposed to.

However, as Dumbledore was not present, they had no choice but to accede to Fudge's demands, as he was the Minister of Magic. So they allowed him in with the dementor, but still never suspected that the dementor would actually kiss Crouch. In general dementors were well behaved enough that they wouldn't kiss someone without explicit orders. Throughout Prisoner of Azkaban there were dementors guarding every entrance to Hogwarts. People must have been passing by the dementors on a regular basis yet no one ever got kissed.

Once the dementor actually attacked Crouch, there would probably be little that McGonagall or Snape could have done. We don't know precisely how long it takes to administer the Dementor's Kiss, but the way McGonagall describes it makes it sound like it was pretty instantaneous. If they hadn't been expecting it they would have been unprepared. They likely did not even have their wands out, and for all we know they may have been behind Fudge so did not have a clear shot right away. By the time they would have been able to cast a patronus (i.e. realize what was happening, take out wand, move into position, think of happy memory, cast spell, have patronus chase down the dementor) Crouch would have already had lost his soul. For all we know they might have cast patronuses, but they were too late to stop the dementor.

Answer 3

While I still believe that @BESW's answer above is and will remain the best in-universe explanation, I found an out-of-universe explanation that is, somehow, more satisfying to me:

If Barty Crouch Jr. would have repeated his confession to the Ministry of Magic, J.K. Rowling wouldn’t have been able to write the “Ministry denies the return of Voldemort”-storyline in the next book. My personal guess is that Rowling liked the Veritaserum-induced confession scene too much to cut it, and then the Kiss was the most believable way to get rid of Crouch Jr. afterwards.

Answer 4

The answer is more simple than that. She is simply a weak person who lacks judgement and any degree of character and courage despite her outward appearance.

There are examples in every book. Here are just a few:

• She allows Harry to be tortured in Book 5 and tells him to keep his head down.
• She always defends Snape and doesn't protect Harry or what is right.
• She doesn't support Harry in protecting the stone.

She consistently demonstrated the opposite of Gryffindor courage and nobility and fails to act on her own to defend others or pursue justice. She is the deputy headmaster and Harry's head of house (his parent/guardian while at school). She is a terrible at all of her various jobs.