The poet Allen Ginsberg once said, "You have many writers who have preconceived ideas about what literature is supposed to be, and their ideas seem to exclude that which makes them most charming in private conversation."
That, I think, is why Kini and Amanda didn't win.
When the judges encourage you to make your work more "sophisticated" or "young," you can do one of two things: (a) try to imagine what the judges mean when they use that term and play to it, or (b) determine what *you* think sophistication and youth means and marry it to your own vision, which is an extension of your own personality.
Amanda and Kini, I think, did more of the former and not enough of the latter.
It's tough, because you're in a competition and ultimately, it's not about who is the "best designer": it's about who the judges thought won the day or deserves the prize. So the judges are ... well, the judges. Creativity is a formidably hard balancing act between your own vision and voice, what the market has seen before and will support, what the mentors and the judges think, mercurial tastes and trends, and how stressed out or good you happen to feeling that day.
If it were easy, more people would be trying it. Congratulations to Sean.