Kugisaki Nobara's return to Jujutsu Kaisen might be one of the most controversial aspects of the series. While her return was unexpected, given her 'presumed' death and hints from the author, Nobara's return to the frontlines wasn't something the fandom accepted. However, her return could be considered 'necessary,' given the death of the strongest sorcerer.
Since the birth of Gojo Satoru, the amount and strength of cursed spirits increased to maintain a natural balance between 'positive' and 'negative.' With his death against Sukuna, the balance was distorted, and to make everything the same again, sorcerers had to return. So, Nobara's return might be considered a necessary move to restore the series' balance of power.
Disclaimer: This article contains potential spoilers from the manga and expresses the writer's opinion.
Jujutsu Kaisen: Why Gojo's death was the biggest foreshadowing of Nobara's return

Jujutsu Kaisen chapter 267 commenced with a focus on an empty facility where Ichiji and Utahime were discussing the awakening of someone, and how it might be too hard for this awakened person to use their cursed spirits. To the fans' surprise, this awakened person was Kugisaki Nobara, whose last appearance was during the Shibuya Incident Arc.
Immediately after waking up, Nobara used her cursed technique on Sukuna's finger, halting the King of Curses' movement on the battlefield. Sukuna's immobility was enough to tell Itadori that his teammate was back to life, so he forgot everything and punched Sukuna like a madman.
While Nobara's return might be the key to defeating the King of Curses, the fans didn't favor the execution of her return. Her death was 'obvious,' given how Mahito's cursed technique had a history of flawlessly killing anyone he touched. Moreover, during a convention before the chapter, Gege Akutami confirmed that Nobara's death was planned from the start of the series.

So, how might her return make a speck of sense in the eyes of the fans? Surprisingly, this had to do with the death of the strongest sorcerer, Gojo Satoru. In the battle of the strongest, Gojo Satoru died at Sukuna's hands, and the world was robbed of its savior. However, his death might have triggered the re-emergence of strong sorcerers to maintain a balance.
Before the birth of Gojo Satoru in Jujutsu Kaisen, the world was ruined by curses. Even the weakest curses spent their lives as overpowered beasts, and no one was there to stop them, until someone reported a supernatural happening. However, things changed drastically with the birth of the strongest sorcerer and the gem of the Gojo clan, Gojo Satoru.

Even cursed spirits that were miles away from the sorcerers were terrified of Gojo's appearance, and avoided doing anything to cause a disturbance. So, the weak cursed spirits went into hiding, and the strongest ones started roaming the streets. All of this could be to maintain a balance between the 'positive' and 'negative' of society.
Gojo's appearance might have negated the existence of weak curses, which caused strong curses to start proliferating. However, with his death, the 'cursed spirit' side started dominating, due to which the 'cursed sorcerer' side experienced a buff. So, Gojo's death triggered the return of the strongest sorcerers who weren't dead at that time, and coincidently, Kugisaki Nobara was one of them.
Analysis and final thoughts
While this might be the most logical answer to Nobara's return, it is speculative in nature. While logic has played a part in Jujutsu Kaisen's lore, branding Nobara's return due to Gojo's death could be far-fetched.
This remains a point the author couldn't answer while his series was ongoing.
Related links:
- The most popular Jujutsu Kaisen theory about Nobara and Sukuna comes true
- Jujutsu Kaisen fans ignored the biggest problem with Nobara's return
- Nobara and Momo's conversation in Jujutsu Kaisen highlights one of the author's biggest authorial efforts