Why did his team sound like a mess?
Simply put, it was Ari's fault.
Because he was afflicted with a mild sense of perfectionism, had complete creative control, and truly wanted this song to be as perfect as he could make it because this was the last time he could come in first place before the final episode, Ari had spent days going back and forth, adding, removing, and constantly tweaking little details.
He still wasn't satisfied, but after spending 6 days on it with only 8 days left to get the performance together, he agreed to stop tweaking it and showed it to the team for feedback so they could start practicing.
And naturally, because his team had less than half a day of practice to memorize lyrics and parts of the vocally heavy song that demanded expert vocal layering, choir-like vocals, harmonies, and so on, it sounded like a garbled mess.
