That's just because the DC area is so spread out. You don't really have to be in DC "proper" to get the benefits of the area. Which I think is different than a lot of other major metro areas. You see the same thing with New York paired with Newark.

An Amazon HQ2 in Northern Virginia would cripple the already strained road infrastructure, especially given Metro's existing difficulties. Dulles seems like an obvious choice given the tech corridor and proximity to IA but 28 and the toll road are incredibly crowded as it is.

Theres 3 different local / state governments to entice competition from with that setup, and montgomery county just lost Discovery which was a huge employer who they were wooing with a serious comp package. So you throw a spender like that into a competitive situation and you might get some insane offer.

Yep, this will start yet another bidding war on our area. For the last couple years we've had a constant back and forth of each region trying to claim the new FBI headquarters.