Ive always put a 2-way blame on it.
Firstly, Nintendo. The way they advertised the Wii. The games they released for that audience. The focus from Nintendo was 80% on the new casual market. Mums, little girls, grandmas and grandads. The market for these games exploded, and a cheap crappy game could sell a Million. Which leads me to...
Secondly, Third Parties. They saw the Wii as a profit machine to fuel the big HD Blockbuster titles on PS360. A little party game could sell 100k units and make a tidy profit, so when they see games like Carnival Games hitting big milestones then the choice becomes obvious. They were blind to efforts like the RE4 port, and let the Wii have spinoff titles instead of the serious big titles, again due to the profits.
The consumer cant really be blamed, because the Wii consumer bought games. Lots of games. Its just the type of games they bought werent necessarily the blockbuster... They were the preschool party game.
Its a double edged sword. With huge success they also segregated a huge part of the market.
