When the Belief Project by Big Hit was launched,
it only had one single female act- GFriend.
Yuju, and to a lesser degree Eunha, had lots of experience singing OSTs.
However , "Hitman" Bang Sihyuk himself chose a fellow company owner to singe the signal song - Lee Jieun, the effective owner of Edam Entertainment.
====
Usually signal songs for a company audition is sung by someone in the company.
However, to the best of my knowledge, IU has never been under Big HIt.
Plus, IU had not sung any OSTs or theme songs since 2011, except for a drama written by the person who wrote "The Producers" in 2020 (not counting unofficial OSTs which were not released.)
So, IU was never the first choice to sing a theme song for a Big Hit audition.
Yet, despite of having a group whose members had a solid history of singing OSTs, Mr. Bang shunned them and went over to someone who owned another company, which was extremely strange.
ANd, I think I can probably guess why he did that - he probably did not want GFriend to leave a mark in Big Hit/ Hybe history when this theme song is sung.
I wonder whether gfriend felt a sense of danger at that point.