Why is Background Character the Strongest Now?

Shivam, a government employee who overcame a difficult past, found solace in anime and light novels, particularly "Transmigrated as a Third-Rate Villain." He admired the novel's thrilling plot, insane fights, god-tier worldbuilding, and especially its heroes, Marcus Ardent and Daelen Vorcrest. However, the story's abrupt and devastating conclusion, which saw the continent erased and the heroes dead, infuriated Shivam. After expressing his extreme dissatisfaction with the author, he fell asleep only to awaken as Ezra Celestrian, the most insignificant side character—a character who was meant to be dead. However, Ezra is not weak. He is, in fact, the strongest human side character, whose talent was so immense that the author killed him early to maintain the story's power balance. Now inhabiting Ezra's body, Shivam, a passionate reader who is disgusted by the author's destructive narrative choices and the deaths of his favorite characters, discovers he possesses unexpected abilities like speaking like a noble and a "Divine Enemy" trait. Believing Ezra to be dead, the world is unaware that Shivam is ready to rewrite the story's broken ending and confront the author responsible for the literary destruction.