> There's actually no reason why it couldn't have fit on a Dual-layer disc. Our only guess as to why it'd be a double disc game is that maybe it was cheaper, and since it is installing itself, there's no need to disc-swap after the initial installation, more or less erasing the biggest annoyance with multi-disc console games.

One possibility was that the optical disk lasers on early Wii units had issues reading dual-layer disks like Super Smash Bros Brawl, causing disk read errors. Nintendo's official laser cleaner disk helped to some degree, and (if I recall correctly) the power of the laser could be increased with software modifications to help.