Obito Uchiha returned to the world of "Naruto" as a result of his deep-seated desire to protect the village and his loved ones. After his death, Obito was reincarnated as a Uchiha child, and his memories were preserved. This allowed him to retain his knowledge and skills, enabling him to return and fulfill his original mission. The return of Obito is a pivotal moment in the series, as it intertwines his past with the present, revealing the true extent of his sacrifice and the complex nature of his character.

The reasons for Obito's return are multifaceted. Firstly, Obito's original goal was to create a world without war and suffering, a vision he believed he could achieve by becoming the Hokage. His death was a result of his failed attempt to stop the Fourth Great Ninja War, where he was killed by Madara Uchiha. However, his death was not in vain, as he was able to preserve his memories and skills through the use of the Sharingan and the Mangekyo Sharingan, which allowed him to be reincarnated.

Secondly, Obito's return is driven by his unwavering loyalty to the village and his friends. Despite his initial betrayal, Obito's love for the village and his desire to protect it never wavered. His return is a testament to his commitment to his ideals and his willingness to sacrifice himself for the greater good. This is evident in his decision to use the Sharingan and Mangekyo Sharingan to save the village from the Ten-Tails attack, despite the immense pain and suffering it caused him.

Furthermore, Obito's return is also influenced by his complex relationship with Madara Uchiha. Madara's influence on Obito's life was significant, as he was the one who introduced Obito to the concept of an ideal world without conflict. Madara's death at the hands of Obito's friend, Itachi Uchiha, left Obito with a deep sense of guilt and a desire for redemption. His return is a part of his journey towards atonement and understanding the true nature of his mentor's beliefs.

Data supporting these reasons can be found in the "Naruto" manga and anime series. In the manga, Obito's memories are preserved through the use of the Sharingan and Mangekyo Sharingan, which are unique to the Uchiha clan. The Sharingan allows Obito to see the future and the past, while the Mangekyo Sharingan grants him the ability to manipulate chakra and perform powerful techniques. These abilities are crucial in his return and his ability to protect the village.

Additionally, Obito's return is a central theme in the "Naruto" series, as it explores themes of loyalty, sacrifice, and the search for peace. The series delves into Obito's past, revealing the events that led to his transformation and his ultimate return. This exploration of Obito's character adds depth to the narrative and provides a more nuanced understanding of his motivations and actions.

In conclusion, Obito Uchiha's return to "Naruto" is driven by his desire to protect the village, his loyalty to his friends, and his complex relationship with Madara Uchiha. His return is a pivotal moment in the series, as it intertwines his past with the present and reveals the true extent of his sacrifice. The use of the Sharingan and Mangekyo Sharingan, as well as the exploration of themes such as loyalty and sacrifice, contribute to the significance of Obito's return in the "Naruto" universe.