There are literally hundreds of examples of people improving their draft status by staying a year. To pretend it's just Nash and Jimmer is ridiculous.
I can't think of any examples of a player who is projected to not be drafted improve his draft stock by declaring early. There are many examples of people who were projected to not be drafted improve their draft stock by staying.
If you want to argue that net money was his goal, then fine, his decision may have been reasonable. If making the NBA was his goal, then it wasn't at all. And of the 5 or so people I've met that play on his level, absolutely everyone of them had the NBA as a goal. I'd be shocked if it wasn't for him