>>44840138>There’s no build up to it in any game outside of the Memory Link.So you're saying that there is buildup to the game it happens in. The only people who would care about this kind of continuity are people who played BW1, so it makes sense to put the plot point in a Memory Link. People that played just BW2 would play the game without any expectations for a Champion, just like the rest of the games.
Besides that, Iris being a prodigal young trainer just makes them more in line with the protagonist trainers. She even says in BW1 that she's kinda like Hilbert/Hilda, having gone on a long journey to see the world and meet many people and Pokemon, while polishing her battle skills.
That, and a major theme of BW2 is passing things onward to the new generation, and Iris is the youngest known strong character at the time. That's why Benga exists too, but Benga would piss people off if he was Champion for being completely random rather than just unexpected like Iris.