it isn't so much difficult to get it.
Here's a timeline about how stuff went
-Beginning of the 2nd part. Kishimoto decided that Hinata has to be with Naruto at the end because, based on info he gathered around himself, Hinata was more popular than Sakura.
-But, meanwhile, he started to develop the romance stuff just after the start of the 2nd part and this romance stuff has more NS hints than others.
-NS had an huge and fantastic development which will bring the author to a logical decision: NS has to be canon
-But he felt sorry for Hinata and must repay her for having loved her Naruto-kun from the beginning. Besides, it would been deplorable for a woman having a change of feelings about sakura's heart in a such point of the story.
-He still hadn't intention to develop NH well in his original story but SP contacted him and persuaded him to make the final movie about NH (since it has always been their dream, they are really Hinata's otaku).
Edited by 六道仙人, 21 December 2014 - 01:54 PM.