Someone probably had it, it most likely just wasn't active and Twitter wrangled it out for him.
What's the point of twitter?Is he setting this up so he can toss out some unfiltered popcorn reactions to Nintendo announcements? What's the point of a public Twitter when you're retired?
He probably has a non compete clausule so I wouldnt expect much in that regard.
He might have just paid for the handle.
So, nobody noticed his tagline (or whatever it's called) yet?
"Retired President/COO@NintendoAmerica. Active business provocateur."