That's a bit reductionist. The problem is Nintendo Ninjas are real. (From the Gigaleaks)
We actually do know ex-hombrew developers, who quit developing homebrew, because Nintendo went after them.
So it creates the problem where, people can't be 100% sure that they are choosing to stop out of their own volition.
I personally believe that yeah, he just grew bored of it. But unfortunately I also cannot fully close the possibility that Nintendo somehow got involved. (not saying that's what happened, I am saying I can't believe with 100% certainty is my point)