You want a spicy take?
Willy Wonka hand-selected four children to deliberately torture to put the fear of god into his chosen successor to make sure Charlie would be too terrified to act out or push back.

Wonka's Slugworth stand-in was present at every golden ticket discovery, implying he knew exactly where each ticket was shipped or—more likely—he planted them. Meaning the winners were all predetermined.

You think it's a coincidence Wonka just HAPPENS to be experimenting with dangerous gum, dangerous TV transmission, and dangerous geese just as he's invited a gum addict, a TV addict, and a "bad egg" to his stronghold?

You think he just HAPPENS to have an entire edible room freshly prepared as he invites a glutton in to wander around?

Wonka built a gauntlet and stocked it with children he was so sure would fail, he had his workforce rehearse catchy songs condemning their failures.

But why spend a fortune to torture four children? Because his ultimate goal was to torture ONE child: Charlie.

Charlie's a wide-eyed moppet who's been wandering by Wonka's factory EVERY DAY, staring in mournfully. What are the odds that Wonka's impoverished, hero-worshiping neighbor just HAPPENS to find the last golden ticket?

He's a patsy.

Charlie's spent his whole life with nothing. He's used to nothing. He's grateful for CABBAGE WATER. He has no political savvy, no human insight, virtually no will of his own beyond wanting to see Wonka's factory. He's a perfect puppet ruler.

Ah, but what if he starts getting ideas once he's sitting in the big chair?

Well, you'd just need to put the fear of god into him early. Show him how deadly factory life can be. Convince him that the only reason he and he alone survived was because he deferred to Wonka.

It's been pointed out in detail that Violet Beauregard should've inherited Wonka's empire by the standards he himself set. She KNOWS candy. She's fearless. She's got an amazing sense of taste. She's business experience.

Ah, but she's willful.
https://evayna.tumblr.com/post/180538142389/violet-beauregarde-shouldve-won-wonkas-chocolate

And we all know what happens to willful little girls, don't we Charles?

He doesn't even ask the parents sign the waver contract, because he knows his "dangerous" factory isn't going to hurt them. Because the entire scenario is carefully concocted to only torture the children.

And how do I know this is all about Charlie? Easy.

Grandpa Joe was in on the whole thing.

What's the first thing Grandpa Joe does after lying in bed for 20 years? Sing and dance.

Who else sings and dances? Wonka's goon squad.

Grandpa Joe has obvious been sneaking out of bed every night for clandestine purposes. And dance rehearsal.

In the tunnel of horror, Grandpa Joe comments "It sure is fun" while everyone else is freaking out. The only other people staying calm? Wonka and his agents.

When Wonka is handing out gobstoppers to the failures, he forgets to give one to Charlie, because he knows Charlie will win. Grandpa Joe has to remind him to keep up the act.

When Charlie asks why Violet won't listen to Wonka, Grandpa Joe tells him "because she's a nitwit." He's already watched Wonka's factory kill one child and blow out another's teeth. Any other guardian knows by know that Wonka is dangerous, but Joe preaches obedience.

When they come to the fizzy lifting drink, it's Grandpa Joe who encourages Charlie to drink, because Charlie needs his own orchestrated brush with death for the scam to work.
And WHO figures out that a burp lowers you away from the deadly fan?

Grandpa Joe.

But why is Grandpa Joe, a man confined to a sickbed for 20 years, working with Wonka to install his grandson as his puppet king?

Maybe he's an ex-employee? Or an old friend from before Wonka closed down everything in his paranoid rage? Maybe, but Wonka cut ties with everyone.

Did he cut ties with everyone EXCEPT this one old man who was so dear to him he him convalescing in a poverty-stricken shack, unable to move and subsisting on cabbage water?

No, you don't keep follow a poor friend for 20 years and never help.

But an enemy? Oh god yes. You watch them writhe after you ruin them. You enjoy seeing your unstable confectionery rob your old foe of their mobility, leaving them to languish in poverty.

Then you mock it.

But who would Wonka be so unrelentingly cruel to? Who would he impoverish? Who would he paralyze? Who would he humiliate by turning his child into an toothless figurehead, utterly obliterating his legacy?

Grandpa Joe is Slugworth.

Beaten. Battered. Broken.

And when Wonka came to him, promised him a way out of crushing poverty, if only Joe offered up his only grandson, Joe bit.

The entire tour isn't about Charlie. it's about grinding the last trace of Slugworth into the dirt.

Mr. Wonka: "Don’t forget what happened to the man who suddenly got everything he wanted."

Charlie Bucket: "What happened?"

Mr. Wonka: "He lived happily ever after."