How did Moody curse Harry's obstacles away without the crowd noticing?

Question

Mad-Eye Moody, as we learn at the end of Goblet of Fire, has been conspiring over the course of the year to help Harry win the Triwizard Tournament. During the Third Task this involved him sabotaging the other contestants and clearing Harry's path of potential dangers.

"You had an easier time of it than you should have done in that maze tonight, of course," said Moody. "That was because I was patrolling around it, able to see through the outer hedges, able to curse many obstacles out of your way. I Stunned Fleur Delacour as she passed. I put the Imperius Curse on Krum, so that he would finish Diggory, and leave your path to the Cup clear."
_{(Goblet of Fire, Chapter 35, Veritaserum)}

The very nature of Moody's work is that it should be undertaken quietly and without anyone noticing - "so that [his] hand would not be detectable in [Harry's] success". As one of the four helpers patrolling the maze Moody was in a good position to act and his magical eye certainly gave him an unique vantage point. Nevertheless, any intervention would surely have been extremely obvious.

Granted, the Triwizard Tournament was an atrocious spectator sport, and the Third Task was scarcely better than the Second Task in this regard. Still, the Task took place in the Quidditch stadium, which was presumably routinely equipped for 360-degree panoramic viewing. The crowd may not be able to see inside the maze but they'd have had a good view of the outside of the maze. A stunning spell is associated with a burst of red light in Harry Potter and Moody's spell may well have burnt a hole in the maze. Other spells would have been equally visible. Regardless, the crowd would have seen Moody pointing his wand into the maze, casting spells and self-evidently interfering with the task.

How did Moody get away with manipulating the task so much? Shouldn't it have blown his cover?

Answer 1

People couldn't see inside the maze

The hedges were twenty feet tall.

A twenty-foot-high hedge ran all the way around the edge of it.

—Harry Potter and the Goblet of Fire

They also rendered the area within much darker, and, whether by magical or mundane means, blocked all noise.

The towering hedges cast black shadows across the path, and, whether because they were so tall and thick or because they had been enchanted, the sound of the surrounding crowd was silenced the moment they entered the maze. Harry felt almost as though he were underwater again. He pulled out his wand, muttered, “Lumos,” and heard Cedric do the same just behind him.

—Harry Potter and the Goblet of Fire

Of course, the task was at night, as well. Together, these factors would make it almost impossible to see inside the maze.

The maze was in the Quidditch field, so it seems likely that students were seated all around:

They walked onto the Quidditch field, which was now completely unrecognizable. A twenty-foot-high hedge ran all the way around the edge of it. There was a gap right in front of them: the entrance to the vast maze. The passage beyond it looked dark and creepy.

Five minutes later, the stands had begun to fill; the air was full of excited voices and the rumbling of feet as the hundreds of students filed into their seats.

—Harry Potter and the Goblet of Fire

Nor could they probably see Crouch

Crouch Stunned Fleur, and Imperiused Krum.

“You had an easier time of it than you should have in that maze tonight, of course,” said Moody. “I was patrolling around it, able to see through the outer hedges, able to curse many obstacles out of your way. I Stunned Fleur Delacour as she passed. I put the Imperius Curse on Krum, so that he would finish Diggory and leave your path to the cup clear.”

—Harry Potter and the Goblet of Fire

The Imperius Curse doesn't produce any light, and Crouch could presumably cast it nonverbally or whisper it. Since it was night, people would have difficulty seeing where he was pointing his wand. Don't forget, he was supposed to be patrolling the maze, so it would not have been suspicious for him to have his wand out.

The Stunning Spell is a little trickier, since it usually seems to produce a flash of red light. Either Moody was very careful to stick his wand inside the maze so no one would see him casting it, or he Stunned Fleur with a different, less flashy method.

It is also possible that people did see the Stunning Spell, but in the darkness thought it had come from a champion or something else inside the maze.

Unless a spectator was looking directly at Moody, assuming Moody was discreet and cast his spell very close to the edge of the maze, all they would see would be a flash of red light. And confirmation bias would probably lead them to assume that it came from a champion, not a guard.

But would it have mattered if they had?

In addition, the purpose of the people patrolling the maze was presumably to keep the contestants safe from dangers inside the maze itself, not external threats. As such, if they needed to keep a champion safe, presumably they would have to cast a spell inside the maze. This would particularly apply to Crouch-as-Moody, who could see through many of the hedges. Even if someone had seen him casting a spell, they might simply have assumed he was doing his job: i.e. extricating a champion from a lethal situation.

Answer 2

The crowd couldn't see what was happening in the stadium. That's why no one knew Moody interfered, and why people doubted Harry's story.

‘Look, you don’t understand what it was like after it happened,’ said Hermione quietly. ‘You arrived back in the middle of the lawn clutching Cedric’s dead body ... none of us saw what happened in the maze ... we just had Dumbledore’s word for it that You-Know-Who had come back and killed Cedric and fought you.’

The walls of the maze were high enough that even in the elevated stands the studends couldn't see inside of the maze.

Hundreds of seats were raised in stands around the pitch so that the spectators were high enough to see what was going on. — Sorcerer's Stone.

While not clear in the books, the stands are most likely NOT the quidditch stands (as thought of from the movies) which are raised high enough to watch the game which is played between 30-50 feet in the air, stands that high would clearly be able to look into a 20 foot tall maze.

For once the movie actually seems to be accurate and may shed light into how the stands are set up.

Here we see the students on stands that are at ground level, at the entrance to the maze. The book agrees that at least where the Gryffindors sat they were able to clearly see Harry and the entrance to the maze.

Harry could just make out Mrs Weasley, Bill, Ron and Hermione applauding Fleur politely, halfway up the stands. He waved up at them, and they waved back, beaming at him.

This is the most logical location because the only thing the viewers can possibly see is the contestants entering, and then leaving the maze.

This would also easily explain how Moody patrolling either side or the back wall would be completely out of view from everyone.

Answer 3

If I recall correctly, there were a number of pretty vicious creatures in the Maze, many of which would presumably need to be ... encouraged ... to stay in the part of the Maze they were assigned to, rather than wandering around at random and/or fighting one another. (It would, after all, hardly be sporting if one of the Champions could wander through an area devoid of monsters and another wound up facing a double share.)

It therefore seems reasonable to assume that Moody was expected to cast the occasional spell, to keep everything in order, even in the absence of a call for help from one of the contestants.