MD and VA are highly competitive and also have a lot of appointments.
Proximity to the Academy and proximity to DC. Heavy on Government employees (both civil servant and contractor), and tons of military personnel, either active duty or retired. So their kids have more insight into the SAs, and can easily travel to Annapolis to see the campus. Plus, they will be close to home. Schools are really strong, and offer higher level, tough classes. And strong athletics for smaller states (by population).
For example with my kid: we're within town liberty radius, are a generational military family (multiple Naval officers), and I went to NAPS, and grew up in Annapolis as a teenager, so had a lot to share with hom about the place. He decided that was what he wanted to do, and went after it.