My guess is they were thinking they would get more third party support (ie: Bioshock Infinite, GTAV, MGS Rising, etc.) and that it would have a bigger impact than it has (ie: Black Ops 2) for this period.
When it became clear that this wasn't the case, I think they opted to push things like Pikmin 3 and Wonderful 101 back into Q2 and maybe even Q3 for W101.
The other thing is Nintendo may have been surprised by the positive reception and attention Wonderful 101 has been getting and may have opted to give Platinum more time (bigger budget?) to work on the game in hopes that it might become a franchise hit. It seems to me that from E3 and the Wii U Experience events that W101 when it was on display tended to have some of the longest lines and has gotten a nice reception from the press.







