For many viewers, an overly powerful character isn't much fun. There's not much suspense or doubt when that character goes into a conflict. The same goes for an infallible character, and it's the same with plain old dominance. For a character to remain interesting or have interesting stories, there has to be built in traits that can be seen as flaws. That will help create suspense and doubt when said character is in any type of conflict.
AJ Styles is in a rare position. As an in ring worker, he's at GOD level. His promo work has improved to where it's not something that can hold him back like in his earlier days but, in fact, can now complement him. His rep as a performer is that he's at a level of greatness we all should appreciate. His performance level has been rewarded by being put over clean by John Cena, which is rarely done, as well as be given a WWE world title run. This all within his first year with the company.
But what about AJ Styles the character?
His rep bleeds into how he's booked. He's as great within the story as we all view him as a performer. So great that he beat the former "Face That Runs The Place", John Cena, clean. And he followed that by naturally winning the WWE World title.
Here's the thing, though: He's a heel.
So if he can win the WWE world title right after cleanly beating the great John Cena, who is a credible opponent for him?
Enter James Ellsworth, and with him all those character traits that can be seen as flaws as I mentioned earlier.
Ellsworth is a squash bucket jobber that fans seem to want to cheer for -- for reasons that some, especially JBL, can't comprehend. Who knows and really who cares why they cheer for him, fans enjoy him so let them enjoy him. But that's why it was such a perfect opportunity for Styles. Because of his rep, fans want to cheer for Styles, despite him being a heel. Well, Ellsworth provided him with an opportunity to get heel heat. Not just heel heat, but also to highlight traits that can be weaknesses.
Styles can beat Ellsworth with one move, maybe less. But that wasn't the purpose of their matches. Styles wanted to humiliate and embarrass Ellsworth. He lost focus with what he should've done. And cause of him wanting to mess around, the guy he was in an actual feud with for his title, Ambrose, used it against him. Ambrose helped Ellsworth defeat Styles. Not once, not twice, but wait for it... Three times. Ellsworth didn't screw Styles, Styles Screwed Styles. Styles obsession in getting to beat up a sloth shaped punching bag, also cost him a match with Ambrose.
Why? Because Styles is a shithead, a bully, an arrogant ass, etc etc.
In Ambrose and Styles final face off in the ring before their TLC title match, Ambrose pointed out how Styles lost focus and didn't realize the real threat that was his title challenger. It was great stuff. Styles, the champ who is in rarefied air, can be gotten to by using his own traits against him.
Something else to consider is the actual feud that overlapped the Styles-Ellsworth feud is the Ambrose-Styles feud. Look how long they've been fighting over the title for -- since the beginning of September. If it was just Styles-Ambrose feuding all these months, no matter how great the performers are, fans would've gotten tired of the feud. We're a fickle bunch. Ellsworth-Ambrose didn't just keep things fresh. But allowed the Ambrose-Styles feud to move in an interesting direction.
Styles-Ellsworth was necessary in some ways. It helped keep the Ambrose-Styles feud entertaining. It helped bring forward character traits that can be weaknesses to "The Champ that runs the Camp". Now future opponents can use that and be a credible threat to him. The feud was surprising in how fans received it. Which helped give Ellsworth an actual WWE contract. But most importantly it was just plain fun and entertaining, which helps all those involved.