NR said, "Don't be fooled folks - no matter what they tell you, there is only one reason why Scott Kelby switched from Nikon to Canon: sponsorship and there is nothing wrong with that. Blame the Nikon USA marketing department for that."
Same thing with many endorsed musicians and their choice of instruments, likely due to great work done by the people in the Artist Relations dept.
Definitely sounds like Canon put in a lot of effort to woo him and took pretty good care of him. It's just business.
Aiya... It's only a celebrity endorsement. Everyone knows that they are all paid for the endorsement. I'm pretty sure Tiger Woods and Lewis Hamilton still excel in their respective fields with or without Tag Heuer, and I'm pretty sure Scott Kelby will continue to make wonderful images with Canon, Nikon, or whatever brand out there.