No disrespect to Diplomacy, I think it's a great game. However I would respectfully submit that chess might have a stronger claim to being "the board game of the alpha nerds". (Or go, arguably, in the eastern world. But despite go's supremacy in terms of complexity, it hasn't captured the world's imagination like chess has.)
There's a reason why chess scenes always pop up in movies and literature featuring, e.g. criminal masterminds vs Sherlock, or the venerable doctor teaching strategy to the protégé. The reason is, chess (rightfully or not) is universally recognized as the quintessential game symbolizing human intelligence.
In my opinion as a former competitive chess player, chess skill actually isn't correlated with general intelligence, in the sense that if you're smart enough to get good at chess, at some point you realize that there are more worthwhile things to be doing with your time. But that's neither here nor there.
My main argument is that if we did a vote among all the world's "alpha nerds" to determine who is the alpha-est and nerdiest of us all, I suspect that current world chess champion Magnus Carlsen might place higher than any of these Diplomacy masters. I have no idea how this survey methodology would work (could anyone declare themselves an alpha nerd, or would they need to be confirmed by other nerds with official titles in nerdy activities?), but you get my point.