The explanation below seems a little dodgy to me, so it was probably due to Nintendo offering to keep the franchise alive on their console since SEGA was probably gonna put the franchise on ice for a while.

“That being said, the console games market is in a state of upheaval, so establishing a new game franchise requires a considerable amount of will, determination, and love. Bayonetta is a brand that we want to see become stronger, reaching the hands of more and more gamers,so we have continued to consult with SEGA, the previous game’s publisher, on how we can make sure this takes place. Our answer was a new partnership with Nintendo." Huh???

http://www.ign.com/articles/2012/09/14/bayonetta-2-devs-respond-to-exclusivity-criticism

Three times better than next to nothing is why we're not hearing about No More Heroes 3. And it didn't sell well on the 360 and PS3 because, the game sucked compared the hack & slash games 360/PS3 owners are used to (DMC, Ninja Gaiden, etc.).

I don't see the majority of the Bayonetta fanbase gravitating over to Nintendo, so I believe it will sell half as much (possibly a third) as the original did.

I never played Bayonetta so how is the sequal even relevant to me?
yawn Call me when Nintendo picks up a popular franchise as exclusive

It was rather surprising, but not really shocking. It's only Bayonetta anyway.

Dragon Quest has been exclusive to Nintendo platforms for several years.  Monster Hunter also seems to be going along that route as well.