Here's why:
* The Tournament itself: It's a dangerous competition between three magical schools (Hogwarts, Beauxbatons, and Durmstrang) with challenging tasks. Harry's involvement, even though he's underage, is the central plot point.
* The return of Voldemort: The tournament serves as a backdrop for Voldemort's return to power. It's not just a school event; it's a pivotal moment in the wizarding world's history.
* The development of Harry's character: He faces his greatest fears and learns more about his connection to Voldemort.
* The introduction of new characters and storylines: The tournament introduces Cedric Diggory, a fellow student and a rival, and the mysterious Mad-Eye Moody, who turns out to be Barty Crouch Jr. in disguise.
The Triwizard Tournament is more than just a competition; it's a catalyst for major events and character development in the Harry Potter series.